I doubt it’s that as what I saw was very old near original sat on top very new hours later… unless the same author in some way is refreshing that old paint but wouldn’t expect that is how its adding detail. I would expect each new blob is separate, despite being the same user - or is it a run of user’s layers, rather than individual paint updates being displayed in order.
I guess however it works it’s a reminder that the network doesn’t understand time.