The dev is the best and most responsive I've ever dealt with. I've never seen a negative comment about his business practices, much less received spam from him (electronic or otherwise). While I can sort of understand a reluctance to provide info that isn't 100% necessary, it's your address, which you've undoubtedly provided to dozens of online retailers over the years. It's your privacy and your right to protect it, but this sounds like excessive paranoia to me (and I get eye rolls from my SO all the time about how careful I am about protecting our info).
BTW, have you emailed the dev and asked why he wants it? This would be the best way to get your answer.