There's reasonable protection against the price of HBD going too low: the HBD->Hive conversion mechanism. It only fails in the case of the haircut. There is currently no mechanism to protect against HBD going too high (with the possible exception recently of the hdbstabilizer, which is being employed now). So the opportunities for each possibility are not the same.

And in such a case, any proposer who feels he is not getting enough can, in fact, create a second proposal to get paid more.

It's too bad there's a double-standard.

That's definitely an opinion, not a fact, and one I disagree with.