Unknown breather ? 2021 KW T680, X-15, auto

Over on an RV forum a member there has a 2021 KW T680, X-15 Cummins, auto shift of some kind. He bought the truck new. Had a company RVH (?) put a bed on it to tow their trailer house.
He went to do a service, and found this breather element mounted up next to the firewall. His dealership says they have no idea what it's for or even is. The owner is trying to trace it, but because that 1/4" air line goes into bundle after bundle of other hoses and wires, he hasn't quite found the end yet.
I got permission to ask here if anyone might recognize this type of element? My 2021 Paccar (Pete) with a X-15 manual, does not have this breather.
What say you?

 

It was mentioned by another RV member something about a P.I.P. (performance improvement package) that may have been done by the dealer? If it is, to me, it does not appear factory approved, as there is no inlet/outlet hose routing. Now I'm kind'a wondering if he has an air ride hitch for his trailer and there is some sort of ride height exhaust porting that the bed maker chose to route out of harm's way?

 

Update. So the owner of the truck traced to the rear axle housing vent. It was ordered as a single axle from factory. Still unsure who installed the 1/4" line all the way to the firewall, but I'm thinking the lube is aerating/foaming excessively and that 1/4 line is trapping pools of lube in low spots.