They absolutely should have. But this is a pretty tense situation with hundreds of thousands of people trying to get out and many people that are refused exit are getting belligerent. Ukraine has decreed a mandatory immediate conscription and obviously that should only be for Ukrainian citizens. It's a very messy situation at the border, waiting times right now are decreasing a bit because there are no more id checks on the Ukranian side (like there were before) so hopefully the flow of refugees will speed up, the wait earlier today was 60(!, not a typo) hours.

This incident likely happened at the Polish border where the lines were longest and there were the most problems, if anybody is still trekking towards the border and they have the choice between Hungary, Romania or Poland I would advise to take the Hungarian or the Romanian route because the lines there are - from what I hear - considerably shorter and there are less problems at those borders.