We don't know what NATO movements in Poland, Baltic states. Russian reinforcements in Belarus could be countering NATO reinforcements in Poland and Baltics, sending a signal to not play tricks against Belarus territory, not necessarily attack Ukraine again from Belarus territory. Also, the element of surprise is completely gone with a Belarus 2.0 springboard, and would only serve to elongate and strain the logistics supply line even further. Russia should just concentrated their forces against a dot, rather than disperse and dilute themselves again.
I think Ukraine has 1 million mobilized, whereas Russia began with 200K, lost +100-150K due to expired contracts, then mobilized 300K, so Russia has ~400K-500K total... (not including Russia's announcement of expanding Russian military to 1.5 million, up from 1 million).
Weren't you the one who suggested that mobolization is impossible because it's economic and political suicidal for Putin? Really, you shouldn't be one gatekeeping ridiculous suggestions.