My understanding is that when an NFT is queried via API and uses IPFS then it is added to the queue for resync’ing.
We have not seen this happen.
This contract 0xa1113cf12dafe3471a4e7f281683dc98d4b1ca6e for instance has a number of NFTs with old token_uri (IPFS) and null metadata. We request them almost daily and they never update automatically.
Manually updating the URI and then Metadata seems to work but I thought this should be occurring as a result of requesting them.