Probably because your JA3 fingerprint does not match any known fingerprint of a public version of google chrome. Im not even sure if you can configure your ciphersuites in TLS Hello with just a lowly extension

That might be the how, but the because/why is that a company is arbitrarily enforcing horrible design decisions by many websites that force users to use specific browsers, and penalize/cripple those who try to work around such nonsense. There has to be a less lazy way of combating bots, if that is even the real reason for them being so aggressive about it (which I doubt - it's going to be about money for major stakeholders in the end).