The opening question here pre-supposes he was concerned. Unless the prior discussion had Gates explicitly saying he was concerned (which I assume it didn’t base

The opening question here pre-supposes he was concerned. Unless the prior discussion had Gates explicitly saying he was concerned (which I assume it didn’t based on Gates asking about a document using the term), then it makes complete sense to me to respond with a question rather than an answer. I’d have probably gone with “When did I say I was concerned about non-Microsoft browsers in January 1996?”