not sure I am buying that, as simply as you state it. I have seen some exotic veneers survive with water based glue, and a couple crack, none since switching to non water based glue. Regardless, it makes more sense to me to use epoxy, or another glue, depending on the application, then to introduce more water into the equation.
If you have a recipe that works, excellent. Hopefully you can explain why I am wrong, in detail.
The moisture on the reverse side, as you say, to me sounds like the same recipe as '200 years with no humidity control'. Based on my observations, and I have only theories still, nothing absolute, I think that in the glue up, there is an immediate swelling, different woods and substrates will swell with exposure to moisture, differently, then, with the '200 years of no humidity control', and all of the water moisture, and probably some additional shrinkage of the cellular structure, the wood is under stress. If the wood is under a lot of tension, like a mixed grain, or a wood that is more reactive to moisture, some other unseen stress, it may crack. Maybe it is a few hours, maybe it is a few months. (like with 2.5mm Cocobolo veneer) You can take 10 different pieces of Ebony, glue them to 10 different pieces of Mahogany with water based glue, how many will crack? 2? 4? none? Woods move when glued, less with epoxy, or resin based glues, then with water based glues. Yes, absolutely, water based glues cause swelling in wood at glue up. In gluing things like an Ebony veneer to some substrate with a water based glue, there is a range of glue amount that will give a successful bond, and using the absolute minimum amount will help minimize cracking/ movement in the wood at glue-up.
Personally, it is so much less work to me to mix up some epoxy, or resin based glue, then it is to remove and replace a cracked veneer.