Don't take offence but I think flinching, of some form, came into play. If the bench shooting caused pain then that would've caused subsequent flinching issues. It's a natural reaction and everyone will flinch given enough shots and depending on the rifle/body angle. I know that I will tend to drop the rifle fore end if the recoil starts getting to me, or even if I start getting tired. When this starts to happen I can sometimes "save" the shot by not squeezing the trigger, but I'll still drop the fore end. Embarrasing but gives me more incentive to stop the behaviour.

Recoil, and gunshot noise, aren't noticed as much with the excitement of hunting.

Another thing that may be worth considering is the body angle when bench shooting. Many people will lean more into the rifle when shooting from a bench which angles the butt more towards the top of the shoulder. The recoil will tend to push more down onto the top of the shoulder rather than pushing the whole upper body backwards when shooting upright when standing.