I would expect it’s significantly more resistant than a soggy piece of bread, as an iPad Pro holds it shape when holding from one corner. A soggy piece of bread would have very little structural integrity. AND the weight of the water might actually lead to a catastrophic failure. Even if you make the iPad Pro soggy, it would still not be as easy to bend as soggy bread.I don't expected it to be unbendable. Of course if any amount of force is applied it will break an ipad or iphone. I just don't expect it to bend as easily as a soggy piece of bread!
I had an iPad Pro to test with, but didn’t have access to soggy bread, so this is just another anecdote as I don’t have the numbers to back my claims.