I can‘t speak to the Allant particularly, but two years ago out on the Erie Canal trail near Tonowanda I rode through heavy downpours all morning, several quite deep puddles and water just everyplace on my Trek XM-700 and didn’t have any issues at all. I did wrap the Intuvia display in plastic, but the motor was on it’s own and did a great job in some tough conditions.
I’ve gone through a few sections of trails with standing water as high as the spoke nipple but no more. No rain yet. I’m mostly concerned about getting stuck in heavy rain for extended periods of time.
I do not own a Trek, but the Bosch e-systems are well tested. They come from Europe, after all, and were designed by and for Europeans who ride more for transportation than Americans. That's why European bikes frequently come equipped with mudguards, racks, lights, bell, kickstand, etc. They are made to be used every day, not just on weekends in good weather. All this is to say that if Trek...or any other big manufacturer's e-bikes...were no good around water, we'd have heard about it.
I haven't ridden through any creeks on the Allant yet, but I did enjoy a recent 30 minute, 8-mile ride in a substantial driving rain (a heavier downpour than typically encountered in my region). No problems at all other than feeling a bit damp afterwards.
Inability to regularly ride in the rain would be a major deal-breaker for many of us who use bicycles as commuter vehicles, especially in wet climates such as the North American Pacific Northwest.
I rode three different e-bikes and have experience with the fourth one (three mid-motor e-bikes: two Giant and one Specialized; and a hub-motor one). It happened to me and a friend of mine to ride into a flooded area so the motors were completely immersed in water. No trouble: Especially mid-drive motors are made as totally enclosed units. I don't expect any trouble with the Allant, either.