Hi !
All 3D applications use slightly different material systems, so there's sadly no standard concerning this. There's always a headache with this. E.g. if you import those file into an other 3D app, they may look fine.. 😞
Honestly, I'd try to create a script which gets rid of all those transparencies in 1 step after import. Takes some time to develop, but this will also help creating a proper pipeline.
Matt