MAX 10 - Erase CFM sector - IP states "successful" yet sector not erased

Is the successful erase status appearing on a read you perform when waitrequest is low? That's the only way to know it's valid.

And what you describe is not the proper implementation of waitrequest in a host. It doesn't have a set pattern. You can issue a read/write command (address & data signals) at any time, but if waitrequest is asserted, you need to continue asserting the command signals until one cycle after waitrequest is deasserted. The command is transferred on that cycle and you deassert the control signals after that point.