User blog comment:B214/Volume 22 spoilers/@comment-109.177.218.233-20160825132203/@comment-9595671-20160827142831

Yeah, admittedly the ending has made it tricky because Issei got his main power up from the Kyoto arc earlier than he should have, and under different circumstances too.

And while Issei got amnesia to keep the Raynare's curse issue from being solved, it's questionable if Rias forgot anything. If she remembers, that could make breaking said curse a bit trickier.