Why is he only honest when he is in heat ?!?!(╯°Д °)╯╧╧

I wouldnt call it honest. Its his pheromones making him in the mood. That's why he hates his heats. He doesn't feel in control.

You have a point but he never shows affection towards his partner and sometimes acts like he hates him (at least that's the impression he gives off) but we know he likes him because they bonded. That's why I said that he's only honest during his heat, although I also agree on what you said.