In most cases a leak will leak at all pressures. Zero pressure would be much slower, but the gravity of the water alone would likely put a nice sized puddle in the engine over the long winter slumber.
The question is: How does the Evans coolant mix with
oil? The water milk shake is well known and easy to recognize.
They make a fair amount of noise about the water, and their willing to mislead you on the fan to sell it to you. I have to say I think getting all the water out is pretty important. I would suggest an old air conditioning man pull a vacuum on it, but it would collapse the radiator, pop the water pump seal, and suck some gaskets out of place with my luck. Draining it hot and circulating hot air through it might dry it out quickly. Blowing dehumidified air through it at room temp for a couple days should get it dry as a bone.