I had the Garbolino g-max which was very waterproof, but on a very wet day a small amount got in Around the zips. I now have the guru and if you lay it zips down it is very waterproof, but not fully waterproof, inevitably around the zips a small amount gets in. Both were/are great holdalls.
Seems that eva is waterproof but zips are the problem area. The question is if your holdall sits in a 3 " puddle would it still be waterproof.
In a raging storm lashing rain then the need will be how to stop water ingress via the zip.