"These good first task have been identified as suitable to get a first approach of our code base for new developers."
From my point of view, tasks marked as good first task are not only bugs, these can also be other simple tasks like "improve docs" or "improve l10n/i18n" stuff.
Reopening: Someone needs to update a bunch of wikipages, potentially the Phab project description, potentially rename https://www.mediawiki.org/wiki/Good_first_bugs yet again.
No, they don't. Those are different and mostly unrelated (specifically, the task tag says "these don't have mentiors, see GFB page on MW.org for things which do". See https://www.mediawiki.org/wiki/Topic:Vbu98p39kwdqmxd8 which I started, which might come to a different answer for that use-case.
Made a few edits on wiki pages which mention the name of this tag and not the name of that mw.org page...