In order for a profile to appear in a project's activity feed on WikiTree, the profile needs to have the project on its Trusted List. as a profile manager. For the project account's Google Group to get notifications for a profile, the project account has to be a profile manager.
In the absence of a Project Leader, it's hard for me to justify adding to the project account's watchlist and management load, except for high-priority profiles (highly visible or contentious profiles). But maybe I'm overlooking something that you are seeing.