As you can read below, I just tried this beta feature. Now, after disabling it, all Entries aside from the newest of a page are missing, i.e. pages with more than one edit today are displayed as if there were no other edits. Log entries are displayed normally. The missing entries remain missing after reenabling the beta feature, and also new multiple edits are hidden.
Topic on Talk:Edit Review Improvements/New filters for edit review
Have you purged your cache?
I’m seeing new changes, so I don’t think there’s a cache in the way. Also action=purge does nothing on the watchlist (normally it would ask for confirmation on GET requests since a few months ago).
Strange. Are you still missing some edits?
Yes, for example when I posted this same request on dewiki’s help desk (WP:FzW), I added it to my watchlist before posting, and saw the change before my post on my watchlist. After my posting, that change disappeared and only my change was listed on my watchlist. And now, after a reply by someone else (which I saw on my watchlist, but then my change was gone) and my reply to that, my last reply appears to be the only change to WP:FzW today.
Translating my response from over there: In the preferences, „Expand watchlist […]“ is still enabled, also the watchlist’s layout is still the one of the the expanded watchlist.
I just tried reenabling the beta feature once more, and now I’m at least seeing all the changes with the beta feature enabled again. But with it disabled they’re still gone.
I’ve got an even weirder problem now: I disabled the beta feature to try removing the GET parameter "urlversion=2", as suggested on dewiki’s helpdesk. But despite the beta feature beeing disabled, it’s still active?!
Nevermind that last one. I had the preferences open for too long, so the change apparently hasn’t been accepted. But even force-reloading the preferences didn’t show the actual state of the setting, only completly reopening the preferences in a new tab suddenly showed it as enabled again, so I could disable it.
Anyway, the suggestion by FriedhelmW to remove the URL parameter "urlversion" was correct, and everything is back to before enableing the beta feature :-)
Thank you for the update, and thanks a lot to @FriedhelmW. I'll ask if there is a way to clean the URL when the Beta is disabled.