The hashing has nothing to do with it. It's just an arbitrary hoop for clients to jump through that filters out the bots that haven't implemented that hoop. So why not just use the client's fingerprint and call it a day? Use their canvas or JA3 fingerprint and I'm willing to bet it would be just as effective.
Most scrapers are unsophisticated, this is why Anubis "works." For this same reason, basic fingerprinting already employed by Cloudflare et al would have the same efficacy.