Poles and Ukrainians have a very strained relationship, which NATO and the USA is trying to contain and control, like trying to sweep spilled mercury. A lot of stuff went on which doesn’t go into standard American history textbooks about WWI and WWII
My various Polish work-colleagues have told me: “we Poles suffered under the Germans, we suffered under the Russians, but we suffered most under the Ukrainians.”
Heard it the same way, from Ukrainians.
Borders in that part of the world are very fluid.