> anyone reasonably clever which spends months studying CTCI, EPI and Pramp and whatever else and doing mock interviews will pass the interview

Spoken like someone who has never interviewed at Google.

I have 6 years experience, a M.S. in CS, have worked at SV unicorns, and studied for 2 months for my Google interview and still failed. Am I an idiot? Possibly, but more likely that the interviews are hard and there is a lot of randomness.

Until you actually study and try yourself, don't talk about how easy it is for anyone "reasonably clever".