YES, a lot dont have a vent plug.
please just use common sense, if you leave them cooking in the sun in 30 plu degrees then you will ask for problems...
if loosening better to fully remove and put a bit of coloured cloth in hole then you know it is out, big damage if you let your board fill with water with half done up plug..
me and mate left our sailboards in car one new years eve, very hot day next, did not get back to cars till midday, sailed and both boards popped their bottoms...
lesson learnt with heat/ plugs and alcohol!!!



