Sorry ... I just want to make a further comment about this:
"... for now the recommended workaround is to tell users to ignore the error unless they’ve encountered a problem deleting a specific item."
That's just not an acceptable outcome. Let me explain why. To following that workaround, every user has to read every Sync Error message, including all the False Positives, just in case there is an occasional Genuine Delete Error reported in the Sync Issues.
The hit to productivity for End Users would be Catastrophic. Besides which, they are just not capable of accurately determining whether something is really Genuine Error or a False Positive.
The end result of THAT is that nobody pays ANY ATTENTION AT ALL to anything in the Sync Issues folder. That, in turn, means that Genuine Errors are missed as all messages are being Ignored.
Please communicate this to the team: errors MUST be worthwhile and accurate, otherwise they get ignored. Its NOT just a cosmetic problem, because the team is NOT taking into account End User Behaviour.
Once we train End Users to Ignore Errors we are in Trouble. That is the biggest reason why this should be fixed, and fixed quickly.