Perfect example of this is how Andrew Lincoln holds pretty much any gun on The Walking Dead. Barrel pointing down, not using the sights. It’s an extreme example, but accurate to be sure.
What I’m getting at is the habit of anticipating the boom before the trigger breaks. When this happens, you are subconsciously pushing the firearm forward and the barrel down.
This happened all the time with my Sig Sauer P250 45 ACP when I first got it. The break point also acts as the safety and therefore it seems like it takes forever to break. My shots were all lower than I aimed. Once I realized this it went so much more on target until I started to get fatigued.