Best guess is that someone in marketing thinks calling them Tiles will make Intel look better because people won't realize they're just following behind AMD in this respect.

AFAIK this will be the first chip where multiple processes are combined into one die, at least for consumer devices. AMD's chiplets use separate dies from multiple node processes all on one substrate so maybe they don't want to confuse it with that.

It isn't on one die; Meteor lake is 4 dies on a substrate.

It's probably a lawyer thing like uncertainty over who owns the noun 'chiplet'.

The interconnect between dies doesn't rely on the substrate though right?

The interposer is the only way the dies can communicate.

Not exactly. The tiles have different functions. AMD's chiplet approach glues homogeneous chips together and uses a center chip to control everything.