The description shown for the Research Assistant is
Edited 50 tag wikis.
According to the List of all badges with full descriptions, this does not include edits to tag wiki excerpts. It's been suggested that the description be updated to make this distinction more clear, an idea I fully agree with. However, that post got me wondering.
Why don't excerpt edits count towards the badge?
When creating the badge in 2012, ex-employee waffles said he wanted to encourage wiki edits over excerpt editing, but this doesn't seem to have worked. Only 5 users on Meta Stack Exchange have earned the badge since its creation 5 years ago.
It seems a bit silly to award users for editing tag wikis, rather than awarding users for contributing to a tag's usage guidelines, which is arguably the most important part ad visible of a tag.