I noticed that after enabling this feature, I noticed that the Tags tab settings are not preserved.
Specifically the Restrict these tag groups to the ‘…’ category and the Require new topics to have tags from tag groups settings.
I had tag groups defined in those fields. After enabling this experiment, those fields were displayed empty.
Strangely though, saving the form as it looked empty, didn’t remove the previously set configuration, didn’t reset the configuration. The fields still looked empty.