Have you used that valve? I have. That valve is fine for pressure relief or to add air by mouth, but it's not effective to deflate a vest enough to swim down then out from under an inverted hull or multihull net. You wouldn't have enough minutes to accomplish that.

A belt cutter that has a protected razor edge, tied to the PFD belt on a short lanyard is a better approach. Something like the Spinlock Emergency S-Cutter. A serrated rigging knife could also do the job quickly, but it's got to be worn so it's handy when/if needed.