sounds like a big flood waiting to happen.
yes, the pressure will be the same on the side walls at a certain depth as it would be on the front/back panels at the same depth.
pressure is a function of water depth.
so I don't know why they would have had the tank built with end walls half the thickness of the front/back panels. perhaps they ran out of money and had to use thinner stuff??
whatever the reason, I would not trust it. it could hold water fine and then one day you come home to a giant mess.