Just because you have to follow the legal team doesn't mean they're making good decisions for the business.

The changes you make to a game engine are almost never the important part of your game's IP.

Depending on who you ask an GPL game engine can only produce GPL games.

I guess you could sell the game ready to play, and then upload its source code without needed assets somewhere else.

Most companies aren’t going to be ok with this.

I know when I write a project, I just MIT license it. If some of the code I wrote helps you get your job done, go for it.