We are employing a similar workaround for detecting and preventing on-device duplicates (building up a list of last-saved values), but last-saved being cleared at form update is a challenge for us (and has certainly led to some personal confusing when testing locally, before I remembered how this works 
).
Is there some consensus around changing this behavior? If so, is it small enough (and not too disruptive) that it could reasonably be included in an upcoming release?