I am not a CGTrader member, but I think there are alternatives to copyright issues. Sites like TS and others have an Editorial License which allows you to publish models even if you are not the owner of the copyright of the brand. And TS, as a big company, is on the spotlight, yet there haven't been any problems with copyright after introducing that license. I don't know the reason why T3DS has not benefitted from that type of license, but again I don't know why the design of the website hasn't changed in a decade. There have been many strange decisions made there. In any case, until a brand issues a DMCA against their own products we are free to sell them under normal licenses. After that, apparently, a different type of license would suffice.
All that is, of course, to my understanding. I do not have any formal training in law.