See in Russian + video: https://bugs.launchpad.net/krita-ru/+bug/1650475 Bundles and custom brushes still have the tags assigned.
Yeah... That's because Timothee removed the old default tags. I'm not sure what to do about it.
Okay, I looked into this and the reason this happens is that we save tags without brushes in the tag file; otherwise unused but defined tags will disappear between sessions. We do that for all tags, including the system-defined tags...
This is a really annoying bug since it makes it a lot harder to switch brushes. Strange thing is there are a few tags that still have brushes, like demo. To new users it must look like Krita has just a few default brushes to offer since the ominous demo tag seems to be selected by default after a new install.
So I looked it up on GitHub and it looks it's kinda fixed already but not yet released or in the repos (I'm on Arch (Manjaro)). As a workaround I - took the the tag preset file from github https://raw.githubusercontent.com/KDE/krita/237509e45aff1c0e8cebd2a5e31815104e449f92/krita/data/paintoppresets/kis_paintoppresets_tags.xml - removed/backed up my installed bundles - copied the downloaded file to ~/.local/share/krita/tags/ (warning this will probably overwrite previously assigned custom tags) - started Krita (all the default tags have their brushes again) and re-imported the previously exported bundles. I hope this helps someone.
I know, it's really, really annoying me too. For 3.1.2, I'm going to have to restore all the old tags, as well as the new tags.
I've now created a system where empty system tags are removed on startup; but user tags, new system tags and old system tags applied to user presets are loaded.