I'm not sure it really matters that it is "external". Because at any moment anyone can choose to look thru the ordinal "lens" or point of view and track an inscription tied to the actual bitcoin protocol. It leaks into real world consequences.

1 sat can be sold for 100,000,000 sats. I don't see how this is not blatantly non-fungible.

This is how I understand it at least. Lmk if I am wrong and why. Haven't done a deep enough dive.