That was the reason that Denver was thought of as a horrible place to pitch.Allegedly
The reason that Denver is a terrible place to pitch has never, ever been about home runs to any player or informed person about the game.
The thin air of Coors drastically affects spin rates. Greg Maddux used to say that he could pick the wings off of a fly with his change up in normal elevation, but he'd have trouble hitting the catcher's mitt in Colorado because he had such spin on his change. He's one of those guys who would likely break all sorts of Statcast spin rate records the way his fastball, curve, and change would move at less than max effort or premium velocity.
Charlie Morton just got done having the postseason of a lifetime by and large due to his spin rate on his sinking fastball and his curve. Both are dwarfed by the same rates for Chatwood. Morton likely made Chatwood a lot of money, but Coors absolutely affected how he could pitch, having to scrap his two best pitches at home and then find the feel for them on the road. It's a pretty insane thing to do to a pitcher.
I'm not sure I would call this a bargain, but Chatwood would have definitely been on my short list of preferred targets behind the top 4 on the market.