Sorry I was supposed to post this as a comment :)

Thanks for the reply. From the users that have told me about the issue they all seem to be on 8.8. Do you know what version of 9 it was resolved in? I'm going to have to put a workaround in my app where I look for all workouts on certain versions of WatchOS 8 & 9 (rather than limiting my app as the source) due to this issue. I'd rather only do this on watchOS version that have the bug as I assuming having a less specific predicate will result in slower HealthKit fetches.