Venting an EPS board is like an "insurance policy" to prevent delamination. EPS boards contain very small air pockets between the foam beads which expand and contract with changing temperatures. If a board is dinged while surfing and water gets in, additional heat (leaving your board on the beach or in a hot car) will cause the water to change phase in to steam and exert pressure on the fiberglass skin - pushing the glass away from the foam (delamination).
It's up you to if you want to install a vented leash plug in your EPS board but we developed the VXVs because so many personal boards were having issues when not vented. Since installing VXVs in boards there has not been a single delam due to water expansion in a board in years.
*It is highly recommended to install vented leash plugs in stand up paddle boards due to the large volume of foam that will expand and contract more in varying temperatures. All the major SUP manufacturers vent their boards with either a vented leash plug or a deck vent.