Just aiming towards this & playing specifically to complete this achievement. I got to the stage I knew I wasn’t going to win my next round & sold all minions bar one to push all of Deryls’ hat boosts together.
Due to the way they were separated my final minion had a total boost of +31 from the hats BUT because 2 came from a triple the game split this over 2 lines so to have
2x hat boost +1/+1
hat boost +29/+29
Showing on the minions stats breakdown, which means my achievement is still incomplete at 29/30.
I appreciate this isn’t a hard achievement, but it’s still a flaw in the reporting logic. The game asks for 30 hats on one minion, which I had, the way they were applied on the minion was separated out which caused it to fail.