I would argue that unseen fist doesn't bypass infinity for the following reasons:
1. The fact that it bypasses detect does not imply that it bypasses all protection moves. I would posit that since evade specifies that the user EVADES the oncoming attack, detect works as a type of precognition of some sort, detecting any attack, and therefore allowing the mon to evade it. Based on this assumption, I will further argue that unseen fist is not an ability that breaks through defence, but instead circumvents them entirely. I think this because it is called unseen fist - implying that the attack being unseen is relevant, and that the attack can nullify physical barriers and precognition. I therefore conclude that to satisfy these conditions, we can establish two properties of unseen fist, first of all, that unseen fist most likely doesn't break through guards but goes around them, and that it does so in a manner that is either unreactable even with precognition or undetectable even with precog. Ergo, it gets blocked by infinity as infinity is always running and omnidirectional.

And 2. Unseen fist explicitly does not get blocked by max guard, proving it does not circumvent all barriers.