If one want to be picky the rule actually word for word states the squig can be released "instead of shooting", yes I know it may be written in that way to make sure people dont try to release a squig and shoot but still.
As Yakface pointed out however the squig attack is a special rule and thus is not really a
CC or shooting attack, its a squig running upp to the vehicle and blowing upp.
Other odd things about the squig:
It does not matter if the squig has a
LOS, it does not matter if the squig has to pass through impassable terrain to get to the vehicle.
The squig will go to the closest vehicle within 18", enemy on 2+ ork on a 1, nomatter what is between.
They are actually rather fun but can cause alot of questions