Yeah, it’s just a way to group those ones together and indicate that they’re the ‘bundled’ plugins. And it also serves as a marker for anyone who has the tag as Watching First Post so they get a heads up about any new ones.
So adding the tag, updating the install blurb, and leaving a fresh post to the plugin topic to say ‘good news everyone 
this is now bundled and doesn’t need to be installed separately, yada yada, remove from app.yml’ is usually the meta portion of things. (Maybe a slightly different flavour if something has genuinely moved into core rather than just bundled as a plugin). Getting that done as close to when it happens is the aim. 
Hopefully an admin dashboard message is also done as well, but that’s another thing.
For a fuller picture, there are still some inconsistencies with how bundled plugins are presented here on meta and in the UI. Some don’t have plugin topics (polls, Discobot, hide details, local dates, etc), and some are hidden from the plugin page on sites as well (chat, polls, Discobot, and so on). Smoothing those out would be nice so it’s more easily understandable for anyone new to know what’s what.