sounding much like they were saying :
5-10%, perhaps.
Yes, it does matter, if you want to correct it.
Right. So you (or, more accurately, those whose job it is) DO and MUST give a toss where the problem lies. Otherwise they can't analyse the data.
If a thorough investigation shows that a problem with the design of the road means that an unusually high level of care and observation is required, then that can usually be addressed. Sometimes it can't, because of physical or topographical reasons.
If, overwhelmingly, it is "driver error" then we could address that fact.
But we won't. Because to try to educate drivers into paying attention to their driving might risk diluting the vitally important message that it's speed and speed alone that's dangerous. Don't you pay ANY attention to anything? "Speed Kills". Nothing else. It's perfectly OK to drive with your head in the clouds as long as you aren't holding a phone in your hand and aren't exceeding the speed limit.
If you STILL have an accident, then it must be because the road's dangerous, so we'd better spend some of that camera revenue on fiddling with tarmac.