FWIW I just recently updated my 1700X bios and there was a 4.0GHz preset OC, so I tried it and it is stable, whereas I only figured out how to get 3.8ish on my own. AMD's bios does seem to have the habit of getting a little better with age, so even if they screwed up with false promises, with bios updates maybe those chips will reach their advertised speeds?
In case anyone is curious about the OC preset, I have an ASUS Hero VI.