Personally I feel like this interpretation is distracting and a bit unnecessary. Doesn't feel like the type of movie where there would be a twist like that.

I need to rewatch before I peg down my feelings about the ending, but on first watch, it's a commentary on how "living your life in the present" (like Padraic) and "leaving a legacy" (like Colm attempts) can BOTH lead to destruction if you divorce one from the other. Like, both men are so unreasonable that they end up hating one another, when some very minor adjustments to their friendship could have literally saved lives (and fingers lmao).