NO, the whole concept of the air sealed container is if they need to pull prints/DNA off the firearm at a later date, if just placed in a vacuum bag loose on a shelf, then someone moving the bags around could end up smearing prints or destroying DNA evidence instead.
So the air sealed pack is to prevent moisture in the storage air from causing addition corrosion/contaminants, and the container part is so the firearm is not handled repeatably handled as well.
Bluntly put, if the firearm needs to go to forensics later, then they less the firearm is directly handled/less contaminants by things around in in lock up, the better they can pull the needed evidence from it.
Simply put, in this day and age, not only can them pull finger prints off the firearm to start with, they may be able to pull DNA from the firearm from someone else that may have been part of the crime from the firearm well.