No, it is just, when you are disarmed and attack, that the MC kicks, and Orcs can then catch her in this specific Sex Position, if the conditions are met. And it is never RNG it is just, that every enemy type, has certain perferences. Thugs only do Vaginal as an example.Oh, I didn't know about the last part, if you are armed it's RNG even if you try to manage desire levels, unless your skill levels help you with that.
Btw, does being unarmed affect more scenes? Because i have completed basically all the content while armed, so it would be a great news for me.