User agent string on Big Sur has OS version 10_15_7.
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko)
This is observed on Safari as well as when programatically derived using WKWebView().value(forKey: "userAgent").
Similar bugs are reported on Webkit Bugzilla too. https://bugs.webkit.org/show_bug.cgi?id=213622 https://bugs.webkit.org/show_bug.cgi?id=216593
When is this expected to fix?