Below your original question, here, you should see the option to Close this one.
It's a great question! I hope everything at the other post helped. I have an account with them for the very reason of wanting some of my concerns with sourcing to be addressed. When a profile gets mangled in one place, it's likely to propagate like weeds. So many of us are in search of truth, but sadly, the process of applying validity tests and adding sources is overlooked when a nugget of "new information" is found, that it's very easy to just repeat it without questioning.
The fact of the strong emphasis and requirement of sourcing applies at WikiTree, plus the fact of managing One Tree from which all relatives are intertwined is why I am sold on WikiTree.
To get specific on your query, though, presumptively a specific DD/MM/YYYY on Find A Grave would come from a birth or death registration/certificate, an SSA record for later records, and in those fortunate cases, an actual visited tombstone. As we all know, tombstones aren't always that specific, and for some, tombstones don't even exist. In modern times, cremation has been gaining acceptance, so unless a memorial stone is erected, official records would be the only source.
Best of luck in your continued research. I am glad that you have chosen WikiTree as your favored repository.