I definitely agree with the Negative form Traits being biddable against you (although I'm still unclear on whether Garou can do so or not); that is clearly the intent of the rules and makes sense.
But if all form traits can be bid and lost normally, that seems at least as logically wonky as them not being biddable. I don't see any reason why a 3 Physicals Garou, after exerting themselves in Crinos, would then revert to Homid (which is perforce weaker, with less strength and endurance) and NOT be exhausted. Maybe being in Crinos, with its super-regeneration and better cardiovascular and muscular strength, was the only thing keeping them standing. That seems perfectly reasonable to me.
Conversely, all of the forms give different traits. If I bid away my 8 Crinos traits and then shift to Hispo, do I have 8 new traits to bid now? That was a super-easy refresh, if so. If I then use THOSE up and shift to Lupus, do I get 5 new traits again? When I spend WP to refresh Physicals after exhausting those, do I get back 21 traits across all forms and get to do it again? This effectively turns the different forms into Pokemon that you rotate out as they get tired, which I guess could be interesting but isn't the way I've seen it done before.
Maybe you can only have one pool of up to 8 form traits, and once they're gone, an equivalent number are gone across all forms? I dunno.