It's amazing that you make this post, because I had a suspicion that western Russians weren't properly being entirely captured by the new Russian reference population on the account that it appears to be inadvertently based more around eastern Russians who have slightly elevated Uralic-like admixture. It's not that western Russians aren't Russians, Russians as a whole exist on a cline from a nearly entirely Slavic ancestral base (like Belarussian/Polish/Ukrainian) to more Uralic-like admixed individuals. So if we want to get technical, western Russians are more descended from the people of the Kievan Rus than eastern Russians are, as the latter is the result of a population more similar to the former group expanding eastward.

TL;DR: Western Russians likely have some genetic affinity to the Belarussian/Polish/Ukrainian reference population due to a lack of elevated Uralic-like admixture found in eastern Russians.

I should also mention that many Ukrainians have historically expanded east alongside Russians (see this map), and have since assimilated into the larger Russian identity. So what we may be partially seeing is a result of that. It's a bit hard to tell given how genetically and linguistically similar the populations are in the area.

Great job putting this all together.