Disparities between `_json` and `User` model.

[changeling]

Playing around with dumping the __dict__s for followers/friends, I noticed the following differences. I can't find a discussion of this in the docs:

Only in _json return: blocked_by blocking entities follow_request_sent has_extended_profile is_translation_enabled is_translator live_following muting translator_type

Only in User model: withheld_in_countries withheld_scope

The last two, I suspect has something to do with whitelisting or my request. But I don't see the _json bits mentioned, and I'm wondering about their status. Are these implemented somewhere I'm missing?