[xXOpkillerXx]

F = ma

Bench press will give you upper body mass and mostly impulsive strength (for that matter) in a pushing motion against mass.

When punching you use that impulsion partly but certainly not Mostly. You get the mass from how heavy you are. The acceleration part comes mainly from punching technique and starts from your feet. The momentum transfer through rotation of the different parts of your body (which bench press builds nothing of that except a few muscle contraction/extension speed) is what will yield the best acceleration for your mass. This is basic martial arts science.

Unless you actually have a big enough dataset to make a definite correlation on bench press max and punch force, I don't believe you can make that assumption with just that info. The people who bench press probably don't Only work on their bench press.

tl;dr, it probably helps, but there's no real evidence that it helps significantly more than other strength workout and no there's no way it helps anywhere near punching technique practice.