I think it is relevant here because it provides evidence on whether other countries are likely to put their foot down against China over things like this.

The Assange situation is very different than this one on many levels. I can't see much similarity. It came across as a poor attempt to defend the CCP with the old "America is no better" trope

whataboutism usually refers to irrelevant things. Given Assange is recent (and ongoing) why is it not relevant?

And relevant usually refers to something that relates to the topic. Again, I ask, what does it have to do with the story?

Its a comparison to us/uk relations, that relates to the topic. It literally refers to the story as "this".

"But what about the US/UK!? They do it too!"

Combined with the fact that the Assange situation is not at all similar, I don't see it as relevant.

Different situation, same behaviour - the trampling of individuals for political gain.

BTW, even the historical example of Russian "and you lynch blacks" to the US in response to human-right criticism is relevant, as exemplified by the export of BLM as a general civil rights movement. The US/UK should still be able to criticise China, but without pretending to be a laudable moral example.

Ah then this is where our difference of opinion is. I can see now why you think it's relevant. For me, I always viewed the Russian responses to criticism as diversionary in nature, meant to just essentially say "Well you're not perfect either!". To me, that is just a diversionary tactic to disregard the subject at hand