I had a calico who would do the same! It took years but eventually she went from being stand-offish to demanding them.

My BSH Daisy does this as well. Of an evening she’s started jumping on to my side of the bed and won’t let me in until she’s had her goodnight belly rubs. I’ve had to start going to bed earlier to make up the time!

My sister’s cat that’s become the family’s cat does the exact same thing. He’ll do the side flop, and if he isn’t getting adequate attention he’ll begin to wriggle really adorably.