You are right. but in the Assetpack metadata is a release Date setting. You could just use this. And once it is "one time" activated, it's not possible to do again (to prevent spaming the "newest" thread).
This way it would just work for games and assets on release.
Yeah so there should be implemented a way that it is not. Or give an option at the project page. Which isn't a big deal regarding html and a bit PHP that pushes to the database.
My suggestion is not to change the metadata but to give people an option to handle their project correctly. Since the behavior right now is irritating and at least in my opinion not right.
So you actually get the "newest" thread when releasing not when publishing a page - it doesn't make sense to see a published but not released project under "newest" - and if it gets published there is no position in newest.
Maybe set an option at the project page as "publish now to newest - or - publish to newest on release". That's what I would propose.