Well that's just not true is it.
The West has had very good intelligence on the war.
I would always be more likely to believe something coming from Western sources than from Russian.
Everything that comes out of Russia is controlled and state validated.
Here, besides governments (which I am always a little dubious of), you also have military history people, ex generals etc.
Sure, we can take things with a pinch of salt, and there is no way I believe everything said by the UK or US, but there is a wealth of info out there from this side and that involves multiple countries. There will always be a varying degree of opinion and disagreement on the info coming out from pretty much anywhere outside of Russia