Is this _only_ figerprinting then? If the profiles are different, do they manage to extract some UID from the profile (which I would assume is a bug in the browser), or do they store data client-side using persistent storage APIs?
It's certainly a mystery, because you'd expect any capability fingerprinting (some combo of UA, extensions, CPU/GPU specs, IP etc) to give an identical result between profiles, so it does seem there's some per-profile difference. But I can't think of any browser API that exposes something like an ID...
It looks like it is using heavy obfuscation.
.... adGuardGerman:[u("LmJhbm5lcml0ZW13ZXJidW5nX2hlYWRfMQ==") ....
I see things hat look like font fingerprinting, CSS, Apple pay detection, ... , msPointerEnabled, ..., webkitResolveLocalFileSystemURL, ... cookie settings... ... used mathematical library (sinus, cosinus, ...) serviceworkers, ...RTCPeerConnection, hardwareConcurrency,
Maybe we could dissect it and analyze the full list?
At some other place, they documented e.g. you can get the light/dark theme information out of the CSS. Doesn't even need JS to do it.