According to your characterization. You're the one who wants to make it about "quality" of source rather than accuracy of claims-- presumably because then being the subject of smear campaigns by imperialist propagandists counts against credibility.
That's rich, considering the amount of time you spend strenuously complaining about the sources others provide. In fact, I love the irony of saying that in the very same post in which you provide a tweet from Mate... in which he... dismisses a conclusion on the basis of its source. It's almost beyond parody, to complain about people doing something while you do the same thing
in the same post.
OK, let's look at the claims themselves, then. Firstly, that the US withdrew OSCE observers. Well,
it's clear the OSCE is still well operational in Donbas, with extensive incident reporting, despite the fact that
Russia withdrew from cooperating with them at all in September, which strangely goes unmentioned. The US
did withdraw its staff from the OSCE centre in Donetsk, however (about 21 people). I mean... with Russia having explicitly withdrawn from cooperating with the OSCE, Donetsk was quite clearly a risky posting. Recall Russia's long history of murdering reporters the state doesn't condone?
We can call that about a... quarter-truth, though it's a bit sick to blame them for withdrawing some staff from a city now controlled by an explicitly hostile military force.
Secondly, we have the claim that Ukraine refused to renegotiate with LPR & DPR. Somewhat undermined by the fact (already posted above) that Ukraine invited them, alongside Russia and the OSCE, to a meeting of the Trilateral Contact Group, which they refused.
Huh, so the accuracy of the claims themselves is kinda bollocks, then. If only a quick look at the source had told me that was likely to be the case from the start and saved me the time.