calling module_invoke vs. function & references

I'm new and was just looking at the core to answer this question myself. The answer is probably coming too late to help you but I may as well post it for anyone else who's curious.

Module_invoke doesn't do much more than call the function but it does impose Drupal's "_hook" naming convention and it checks that the function exists before calling it.

Module_invoke wants the first argument to be the module name, the second the hook, and then whatever arguments the function takes. For example:

$block = module_invoke('user', 'block', 'view', 3);
print $block['content'];

Returns something like:
There are currently 1 user and 0 guests online.
Online users
* admin

It's asking the user module to display its block #3. Same results from: $block= user_block('view',3);

I pasted in the relevant core code for the module_invoke function below. (from module.inc, v4.7 RC1)

For people unfamiliar with all the PHP used below:
• func_get_args: crams whatever arguments were passed to the function into an array
• array_shift: returns the first item of the array and removes it from the original array
• call_user_func_array: calls the function, using an array to hold the arguments

function module_invoke() {
  $args = func_get_args();
  $module = array_shift($args);
  $hook = array_shift($args);
  $function = $module .'_'. $hook;
  if (module_hook($module, $hook)) {
    return call_user_func_array($function, $args);
  }
}

function module_hook($module, $hook) {
  return function_exists($module .'_'. $hook);
}