what do you think the glue to hold the vinyl floor does when you have it installed..... seals the floor.
so if you got water under your laminate floor. it would have to penetrate the cushion which is installed under that laminate flooring. then make it to the subfloor. there it could sit and swell the sub floor before evaporating. if you sealed the sub floor, the water would sit there longer possibly causing a mold problem. to make my point either way will work, just be aware, a water leak will do damage if you get one... the type of damage will vary due to the construction method used...
glue/seal or not to seal... whatever makes the floor look and last the longest.