Filtering by User Relationship Type in Views only works when the filter is in the Default view.

And actually, this is also true for exposed filters in the User Relationships view type. An exposed filter will only display if it's in the Default display, ignoring other displays.

This is one with the filter in the default view, so it works. However, just delete the exposed filter, and add it back in the Block display, overriding the default, and you'll see it does not show up.

$view = new view;
$view->name = 'my_friends_full';
$view->description = 'Friends on the profile';
$view->tag = '';
$view->view_php = '';
$view->base_table = 'user_relationships';
$view->is_cacheable = FALSE;
$view->api_version = 2;
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */
$handler = $view->new_display('default', 'Defaults', 'default');
$handler->override_option('relationships', array(
  'requestee_id' => array(
    'label' => 'requestee',
    'required' => 0,
    'id' => 'requestee_id',
    'table' => 'user_relationships',
    'field' => 'requestee_id',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'none',
  ),
  'requester_id' => array(
    'label' => 'requester',
    'required' => 0,
    'id' => 'requester_id',
    'table' => 'user_relationships',
    'field' => 'requester_id',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'none',
  ),
  'content_profile_rel' => array(
    'id' => 'content_profile_rel',
    'table' => 'users',
    'field' => 'content_profile_rel',
    'relationship' => 'requestee_id',
  ),
));
$handler->override_option('fields', array(
  'picture' => array(
    'label' => '',
    'alter' => array(
      'alter_text' => 0,
      'text' => '',
      'make_link' => 0,
      'path' => '',
      'link_class' => '',
      'alt' => '',
      'prefix' => '',
      'suffix' => '',
      'help' => '',
      'trim' => 0,
      'max_length' => '',
      'word_boundary' => 1,
      'ellipsis' => 1,
      'strip_tags' => 0,
      'html' => 0,
    ),
    'imagecache_preset' => '5',
    'exclude' => 0,
    'id' => 'picture',
    'table' => 'users',
    'field' => 'picture',
    'relationship' => 'requestee_id',
    'override' => array(
      'button' => 'Override',
    ),
  ),
));
$handler->override_option('sorts', array(
  'login' => array(
    'id' => 'login',
    'table' => 'users',
    'field' => 'login',
    'relationship' => 'requestee_id',
  ),
));
$handler->override_option('arguments', array(
  'requester_id' => array(
    'default_action' => 'default',
    'style_plugin' => 'default_summary',
    'style_options' => array(),
    'wildcard' => 'all',
    'wildcard_substitution' => 'All',
    'title' => '',
    'default_argument_type' => 'user',
    'default_argument' => '',
    'validate_type' => 'numeric',
    'validate_fail' => 'not found',
    'break_phrase' => 0,
    'not' => 0,
    'id' => 'requester_id',
    'table' => 'user_relationships',
    'field' => 'requester_id',
    'override' => array(
      'button' => 'Override',
    ),
    'relationship' => 'none',
    'default_options_div_prefix' => '',
    'default_argument_user' => 0,
    'default_argument_fixed' => '',
    'default_argument_php' => '',
    'validate_argument_node_type' => array(
      'blog' => 0,
      'page' => 0,
      'story' => 0,
    ),
    'validate_argument_node_access' => 0,
    'validate_argument_nid_type' => 'nid',
    'validate_argument_vocabulary' => array(),
    'validate_argument_type' => 'tid',
    'validate_argument_php' => '',
  ),
));
$handler->override_option('filters', array(
  'approved' => array(
    'operator' => '=',
    'value' => '1',
    'group' => '0',
    'exposed' => FALSE,
    'expose' => array(
      'operator' => FALSE,
      'label' => '',
    ),
    'id' => 'approved',
    'table' => 'user_relationships',
    'field' => 'approved',
    'relationship' => 'none',
  ),
  'rtype' => array(
    'operator' => 'in',
    'value' => array(
      '0' => '2',
    ),
    'group' => '0',
    'exposed' => FALSE,
    'expose' => array(
      'operator' => FALSE,
      'label' => '',
    ),
    'id' => 'rtype',
    'table' => 'user_relationships',
    'field' => 'rtype',
    'relationship' => 'none',
  ),
  'title' => array(
    'operator' => 'contains',
    'value' => '',
    'group' => '0',
    'exposed' => TRUE,
    'expose' => array(
      'use_operator' => 0,
      'operator' => 'title_op',
      'identifier' => 'title',
      'label' => 'Search Username',
      'optional' => 1,
      'remember' => 0,
    ),
    'case' => 0,
    'id' => 'title',
    'table' => 'node',
    'field' => 'title',
    'relationship' => 'content_profile_rel',
  ),
));
$handler->override_option('access', array(
  'type' => 'none',
));
$handler->override_option('cache', array(
  'type' => 'none',
));
$handler->override_option('title', 'Friends');
$handler->override_option('use_ajax', TRUE);
$handler->override_option('items_per_page', 30);
$handler->override_option('use_pager', '1');
$handler->override_option('use_more', 0);
$handler->override_option('use_more_text', 'See More');
$handler->override_option('distinct', 0);
$handler->override_option('style_plugin', 'grid');
$handler->override_option('style_options', array(
  'grouping' => '',
  'columns' => '6',
  'alignment' => 'horizontal',
));
$handler->override_option('row_options', array(
  'inline' => array(
    'name_1' => 'name_1',
  ),
  'separator' => ', ',
));
$handler = $view->new_display('block', 'Block', 'block_1');
$handler->override_option('exposed_block', TRUE);
$handler->override_option('block_description', 'Display user\'s relationships grouped by relationship type');
$handler->override_option('block_caching', -1);