Opening data base giving me winning end game moves

I misclicked the opening database for my daily game and to my surprise it is suggesting winning end game moves. I assume this isn’t intended. If it’s not, there should probably be a cut-off for the database after a certain amount of moves have been played.

It's showing matching games in the database. That's permitted.

In Daily games, database use is allowed for any portion of the game. If players want to follow a previous game that far, they can. The restriction is that engine analysis/evaluation can't be part of the database

Then I suppose my gripe is with the fair play rules then. I just hope this isn’t a common occurrence. Because I wouldn’t be that bothered by it if so.

That standard is very subjective and does not even make sense. There are many variations in chess where even moderately strong players know certain lines to more than 20 moves deep. Such as lines in the Sicilian Dragon or Najdorf, or King's Indian Defense - just to name a few.

You can use databases, videos, articles, books, etc on any portion of Daily games, given that restriction against engine analysis (and endgame tablebases are also not allowed). That’s part and parcel of correspondence chess, which Daily is.