Real reason: The Guardian can't handle when readers community note them using.. The Guardian.
https://twitter.com/MarioNawfal/status/1821189070401249385/p...
replies(10):
https://twitter.com/MarioNawfal/status/1821189070401249385/p...
Thus, they tend to reflect the biases of the kind of people who most want to (and have time to) write and approve community notes, drawn from the pool of people who use your site.
By your definition those also must not be impartial and maybe that is a fair definition but what does it imply?
Do you similarly distrust democratic outcomes, jury decisions, etc.?
Voters are partial to the candidates they vote for; that's why they vote for them.