So, in one important vein, I would disagree, but I'm not sure how well it applies to this scenario -- if you are building a system based on deniable encryption, one example that totally falls apart if one party can prove that they have (forced) zero-keying I imagine would be in deniability, especially if part of the zero keying depends on unpredictability of the keyspace of more than one actor.

AKA, if the deniability of your protocol depends on the random keyspace of more than one actor, a vector that allows some actor to compress the space of permitted keys could allow an inference of more-likely potentially valid keys vs invalid keys, thus disproving or at least weakening the deniability of the protocol.

As for the malicious peer problem -- the malicious peer is the very model of state-sanctioned surveillance. I think it would be an exercise in willful blindness at the least to pretend that does not exist.