You're right, "interested in Hashcash" describes dozens of people, and has been a known Satoshi filter for years.

The new claim is more specific: between 1997-1999, Back proposed combining Hashcash with b-money, adding inflation adjustment via increasing computational difficulty, and using hash trees for public timestamping.

That's most of Bitcoin's architecture in one package, a decade early.

The number of people who proposed that particular combination of ideas is much smaller than the number who were merely interested in Hashcash.