I usually try to cite multiple sources because one or all may be biased, but it's less likely that multiple sources will misrepresent reality in exactly the same way.
It is possible, but it is less likely.
I quoted all three in my original response, and he only responded negatively to the one based in UK, implying that he considered the other two met some minimum standard of quality.
He also quoted those same sources in his responses to me. If he thought the same way you do, I would have expected him to dismiss them outright, like you are.
The NPR article I linked above was citing a Russian source.
The AP article was citing Russian legislation, which I assume (and I could be wrong) is public record.