How much GNU is there in GNU/Linux?

That's as may be, and I've never seen anyone contradict it. However, that's not the FSF's position, which is that the use of GNU's compiler, shell, and the various userspace utilities which made up GNU's output in the early 90s constitutes the labelling of the resultant system as a "variant of GNU". The reason those things were used back in the day was that they compiled on the 386 and were available for nothing. Until it became obvious that Linux was the best vector for getting the FSF's message across, it was commonly understood that the two were orthogonal. That this is no longer commonly understood is not because it were never true, but rather because the FSF has spent nearly two decades attempting to obscure this.