5G NR Network Collision Avoidance
IEEE 802.11 is not related to 5G NR, so consideration for WLAN networks following 802.11ay don't apply to cellular infrastructure.

I don't know what "ad-hoc" modi 5G NR brings; I don't think it's any.

So, 5G doesn't do any collision avoidance, because it's not a problem it has: it's a cellular standard that defines that the basestation / cellular infrastructure defines who sends when, where. The mobile network operators own the spectrum, so there's by definition no uncooperative users.

Generally, whereas interference mitigation is in fact a non-negligible topic for coordinated microwave networks, with these deci- to centimeter waves still taking many non-optical paths and receiver sensitivity being high enough for that to create "unwantedly far reach", you can basically ignore that for cellular mmWave applications, where you can be pretty sure that you, as the owner of the used spectrum, will have a relatively easy time making sure that your own femtocell base stations don't lead to mutual interference: The propagation is pretty much optical, so, the potential numbers of base stations a single handset might reach is pretty limited by lines of sight and a pretty small radius.