I wonder if it is a problem with SketchUp on my Mac? I downloaded version 16.1.1451 last night. I have put it on two Macs and the same thing happens.
I just took your fictional_15 stadium and exported it and tried to put it into OOTP. The textures are better, so that is something I'm doing wrong there.
But, the scale of the stadium is still off, see below:
