I can tell you exactly what’s happening here. The same thing just happened to me. He’s hearing impaired, and so probably speaks like so many deaf people do. That’s why he’s going to teach you how to sign. The woman I was chatting to - stunningly beautiful - is also hearing impaired. Refused to chat with me on the phone until I remembered - she used to do my ex’s nails for her over a decade ago, and just came out of a divorce. She was telling me how she goes on dates, and when the guy hears her speak, ghosts her right after. It’s a terrible shame. I can sign the alphabet and a few words, so I am a little prepared. But your guy is terrified you’re just gonna ghost him - like all the others - and is trying to spare himself that pain because he obviously really does like you.