It's a weird one this - I've bought loads of the wheels available and only get a couple to choose from on each model. I think it may be to do with the availability of the specific wheel model in certain sizes/offsets/fitments, which ones are available in centrelock versions, stuff like that.
Not allowing the TE-37 on the GT86 is odd, but maybe it's because they're specifically the Ultra version which is only available in 19" - it might be a requirement that they can match the OEM size to be allowed, even if you'd probably size-up in the livery editor.