I had thought of this too, but a quick check with Angus’ fork, it doesn’t seem to have any data migrations done. https://github.com/angusmcleod/discourse-question-answer/compare/main...discourse:discourse-upvotes:main
This feels like data contamination from old Q&A posts as you said. I also find it funny that this is popping up now given that that migration is from Nov 2021 – I suppose this is because JayJay is only switching to the new plugin now? In any case we’ll have a look at that migration again.