> I always assumed that when I tell p2 to install an IU, it only looks if it already has an IU with that name and version
> p2 will use the checksums in artifacts.xml too:
I don't think so.
The issue is not about how p2 behaves, it's more that for a given id/fully-qualified-version, only a single artifact should exist. Otherwise, there situation is very error-prone as one cannot ensure which actual content they have.
Having published artifacts with same id/fully-qualified-version but different content must be considered as a bug.