You're not wrong, but at that power level anything longer than a short pulse is going to vaporize the stuff in the way.
They probably take that into consideration and pulse the lazer before giving a more consistent shot.
Clearing out the path before shooting the shot.
Maybe they have a ring around the primary shot as well. Vaporizing the stuff that could get in the way of the primary attack.
These people are smart. It's easier to assume they've taken that into consideration