Source language for strings from views defined in code.

The hook_views_default_views() can be used to define views in code.
Some contrib modules implement this hook, e.g. commerce_cart or admin_views.
And of course exporting a view to a feature will create such a hook implementation.

With i18nviews, labels defined in these hooks will show up in the list of translatable strings in admin/config/regional/translate/translate.
E.g. the string "Content" for admin_content:default:title (not sure this is coming from i18nviews).
Or the string "Customer Statistics" for views:commerce_reports_customer_statistics:default:title

The way that i18n_string works, the source language of such strings is assumed to be the site default language, which can be different from English.
E.g. on a site where the default language is German, i18nviews will assume that "Content" or "Customer Statistics" is in German, and allow me to translate it to English.

Is this the intended behavior of this module? Or is a bug? Or an inevitable flaw of the way i18n_string works? Or did I miss something.

I am opening this in the i18nviews queue because here I can describe a clear example.
But I imagine that similar problems occur with other components of i18n_string.
See also https://drupal.stackexchange.com/questions/249057/problem-with-i18n-stri...