Sites can detect I am on MacOS when I turn on Javascript

[Not_Ambrose]

Recently I was on the site obsidian.md

Without Javascript, the site believes I am using Windows (which is intended behavior)
Somehow, though, when I turn on Javascript, obsidian.md is able to detect that I am on MacOS - which should be bad for privacy, because now some users are detected to be on Mac and others are on Windows.

Am I understanding this correctly?

JS OFF

JS ON:

[thorin]

We do not try to hide the OS, as this is impossible, and it causes too much breakage. We limit to two OSes in headers (windows or android) but four OSes in JS/navigator (windows, android, mac, linux).

you can read more about why headers was done like this at Make User-Agent request header match RFP's navigator.userAgent (#234) · Issues · The Tor Project / Applications / Mullvad Browser · GitLab