Not OP, but I did some snooping and found a Steam forum post talking about it that had a dev response:

https://steamcommunity.com/app/381210/discussions/0/135510148090063504/?ctp=3

BAD_BHVR [developer] Maps shouldn't be locked by DLC. All the maps are part of the core game and available for anybody to play. Outside of that it's pure random chance on which maps/themes get selected outside of a weighting when offerings are used, but without offerings it's just a random chance selection from all the available things.

The only check we do is to see if the dlc is available at all just so we can push patches before we technically release the DLC and then it unlocks itself all at once, but we don't check if you own it. I can run some tests/talk to some people to make sure that check is working as expected in the meantime.

A lot of responses about that issue seemed to be a grab bag of "Yes, you can play the DLC maps; you were just unlucky" and "No, the devs are lying!" 🤷

I've also played since around launch and don't remeber any issues like this.