Yes, but the 737 has been around since 1967, which is what the person your replying to was talking about. Going between the 737 NG and the 737 Max would not be

Yes, but the 737 has been around since 1967, which is what the person your replying to was talking about. Going between the 737 NG and the 737 Max would not be a big change even if they were different type ratings, but going from say some turboprop to a 737 would be a big change. If this pilot was moving up to the 737 from smaller aircraft (which nothing says he did, its just speculation), it seems somewhat likely that he transitioned from either their retired turboprops or the Q400 fleet they have.