pretty much a non issue....
1. it is a close range fast target acquisition sight... so most people will not notice a shift of a little bit.
2. ammo will behave differently with that much variation in the conditions anyway.... so as long as you zero in the conditions you are fighting in... you likely won't have a problem.
3. you should confirm your zero often if you rely on your weapon for real life (or competition) regardless.
4. -40 and +50 is a massive range for an electronic device that is designed to be under forces such as recoil. (expansion and contraction or circuit boards and other parts, etc)
ps... A $50,000 truck can have trouble starting in -40 without a block heater..... and can overheat at +50... why should a $500 sight be perfect?
(I know... apples to oranges... but hey..)
Sssssh...they are junk and I'll be kind enough to take one off someone's hands at a decent price so they can upgrade to something better...