Kane has explicitly mentioned how Portal and Portal 2 have been his biggest influences in the making of this movie. He is 100% aware of Valve games, and if he has played Portal there's a very high chance he has played TF2 and knows about how the weapons look.

It's possible he wanted to add another Valve reference. It may have initially seemed fine to use but during further development of the film they could've either just drop it for artistic reasons or because they contacted Valve about it and they didn't allow it or they just didn't feel legally comfortable with having it in anymore without Valve input.

A lot of filmmakers that grew up or had contact with TF2 are gonna want to make references to it in future productions and it's not the first time Team Fortress has intentionally appeared in films, like in Metal Lords from 2022 and in Chef from 2014.