I just use it to waterproof some stuff. But yeah I had the same concern as you, that's why I went with a more high-end waterproofer that I knew wouldn't do anything to darken the suede or **** up the material in some other way. Used it on a few common projects, botega venetta boots, and 750s and they were all fine after application. I think a big part of it is also making sure you aren't just spraying things down until it soaks into the material. Like spray painting, a few light coats is almost always the way to go.
These days I just don't wear anything nice on days it's going to rain or I'll wear my beaters if I'm going to a bar or something like that.