But consider what the alternative looks like: People randomly see unexpected options in their apps, go to look for information about them, and don't find anything, or find some random Reddit discussion where no one is sure what's going on.
A proper announcement done the day of the release, or an embedded notification like what Firefox already does (a "What's new" tab) that can be easily dismissed without any "Reminder me later" cr*p solves the issue.
I guess you could quietly update documentation at the start of the rollout, then make the blog post at the end.