I may be misremembering but this is what happened with recent the Open Gaming License fiasco.
As I recall, they inevitably changed the current one with a clause saying “we explicitly can’t pull the rug out from folks anymore with this license”. Simply ensuring that while they can create new licenses for new content, that can’t mess with creators who adopted the previous one.
Unity did just that the last time this happened, in 2019: https://blog.unity.com/community/updated-terms-of-service-an...
They silently deleted the then-added clause allowing you to use the ToS you agreed to before this most recent attempt.