The OAD website has a link for application note that does not work, so I looked at what Gore says about their GAW 334 membrane...IP68...2m@60 minutes. Has the OAD team done any independent testing? If so what are the results?
As a scuba diver I take issue with the word "waterproof" as do many manufacturers of diving equipment. Suggest you use the word "water-resistant" and give the IP rating, if you know it. Even Gore doesn't use the term "waterproof".
I've fixed the links. The link to the standard case is for the original version that used a Porelle vent which is no longer manufactured. This will be updated in due course.
Can you post a photo of the white vent? Where did this case come from?
The vents should look like this: https://groupgets.com/products/replacement-acoustic-vent-for-audiomoth-case?_pos=4&_sid=0c71c2625&_ss=r