KH1 did.
KH1 said that Purebloods were the result of an experiment that Ansem started and quit. Kh2 said that Xehanort then took on the name Ansem and created the Emblems.
At no point until BBS did anything remotely say that the Heartless always existed.
1. KH1 characters did... Nomura did not.
2. You need to understand that Heartless were rare until Xehanort caused havoc in all the worlds. It's easy for the characters to mistake that the Heartless weren't made by Xehanort. The characters don't know everything. Heck, Ansem himself talks in KH2 how much of his research and theories about the heart became failures and many were proven to be wrong. Remember the quote "We're both ignorant... as oblivious as when we began."