Exactly. That is the purpose of the bungee loops in many of the available pockets - a great improvement - as you can just pull everythiing out of the pocket and sort it out outside the pocket if need be.If you clip everything into the pockets with double-enders and bungee, you dont lose much even if they come open
Also, with velcro you are not limited by the pull angle on the zipper and unlike a zipper, things to not get hard to open if the items rearrange themselvse and press against the top of the pocket.
Now...if we were ejecting underwater at 500 kts or something, I'd say go with zippers, otherwise, the added security and complexity of a zipper just creates one more thing that can go wrong.