Russian expansionism would not be like ideology driven Soviet expansionism. White Russia doesn't need to spread ideology to other nations (Soviets IOTL were obsessed with possibility of German communist revolution, that would help them to spread communism over whole Europe), White Russia simply have less ambitions and Russians were already aware, that keeping Poland is troublesome. There could be border tensions over Volhynia and Western Belarus, but these lands are not worth much, they're money sinks. Poland took so much IOTL after experience of Battle of Warsaw to keep Soviets as far from capital as possible and to eventually trade some of these lands for peace or for gains in the west. And if Poles had to choose between Corridor and Eastern Borderlands, choice would be obvious.