KYC serve its purpose for the good sites, and we know that fraud really exist in gambling.
Well, having a fixed wagering requirements can be a good one but that doesn’t mean your account can’t be audited or ask anymore. Most of the wagering requirements is not that high and easy to achieve, the site should make a clear rules with regards to this one and inform the players if there’s a changes.
For the good sites? What do you mean precisely? What do you call fraud in gambling exactly? Except through fixed matches which only concern sportsbooks I don't know what fraud you can commit at gambling. Yes it certainly doesn't mean your account can't be audited and more can be asked but it's very less likely to happen which such kind of requirement.