>Nah, Spur (a company tracking residential proxies) doesn't flag it at all.

I looked into it and so far as I can tell it works off a blacklist system, rather than any sort of automatic analysis (eg. TCP or MTU fingerprinting). If you set up a "residential proxy" in the form of a home VPN, it won't be detected. It also means the detection is only as good as whatever their backlist source is. If it's a niche provider, it might not get picked up at all.

They're not doing a very good job at it, tried a few disposable free residential proxies - not flagged. Tried my CGNAT home connection - flagged. My phone connection - also flagged.

Maybe he is doing it for fun and not actually trying to hack the website with Rick Astley lyrics?