With my understanding of Bitcoin, I still don't get the NFT thing.

Why not just timestamp an encoded hash of a file instead.

Ownership of the file can be proved by reproducing the hash(offchain).

And the timestamp prove since when you own the file(on chain).

Then if the file owner change, it can be sent privately and the new owner rehash the same file, thus invalidating the previous owner.

Optimized blockspace!

No limits on size or file type!

Can be done without reveiling the file to everyone!

If you don't want your jpeg to be stolen, don't put it on the internet!

Did I miss something?