Sorry, but this is bollocks, if some western countries want to send in 'peace keepers' they can define & frame that operation as they wish, they could reinforce the reason for going in by the fact they are protecting international investigators into war crimes, and even invite Russia to send their own investigators to assist in those efforts.
The west of Ukraine has never been under any credible threat by Russian ground forces, so there's no reason why that shouldn't be secured as a safe haven for those displaced. And, as Russian troops have retreated from the north, the same applies.
Yes a lot of Ukrainian forces have been focussed on the east throughout, but they have been struggling and now Russia is planning to up their game in the east & south, so there's every reason for Ukrainians to do likewise, otherwise they are going to get fucked.