That's BS. Had an account last year (bought an account for that specific reason) to use wallhack on. Why? To see myself on demos after and hopefully learn some shit since I'm addicted to watch OW. Took me a whole ~10 rounds before I got VAC.
It depends on cheat I would say, if it's free, public, private or whatever.
I used a private cheat, it was a WH that worked like the x-ray function on GOTV.
TLDR: You will never be "clean" or in the "safe zone" if you've cheated.