Interesting perspectives. I think some of the discussion is confusing flip, which happens before the projectile(s) leave the barrel (otherwise it would not impact where you hit) with recoil. Recoil is always going to cause some upward movement of the gun, but if that had an impact on point of aim, then all guns would shoot high.
Not sure how important it is in the grand scheme of things. Re Churchill and his XXV guns, part of the discussion that caused me to post the question was the contention that shorter barrels don't flip as much as longer ones. Which seems to run against the belief that longer barrels are an asset in target guns.
