just playing devils advocate here, but if only one vendor is conforming to these standards - could it be that the standards are heavily biased towards their implementation?
I tend to suspect that NVidia just invests far more in software than their competition. Hopefully now that AMD has money that will change.
Are you implying that they did a bad job and added the wrong GPU support to ISO C++?
Or maybe that Intel and AMD don't care about C++, and either added GPU support to it that they could not implement, or don't care about adding C++ support to their GPUs?
Playing devil's advocate here, no matter how you want to frame this, it just does not look good for Intel and AMD.