Holy moly you're growing monsters over there! I have also heard that higher temps, shorter incubation times leads to smaller, less vigorous babies. Apparently thats not true either!
That is an interesting theory to me. I would like to see some solid data behind that. I think the initial size of the egg laid and genetics/health of the female has more to do with hatch size, no matter what the incubation temp. For example, if the egg is smaller because it's the female's first clutch, or she is crashing and not getting the nutrients she needs and it is incubated at 84 degrees, it may end up hatching smaller just because of all the reasons I listed above. That's my though.
What seems more logical to me is incubation time has little effect on the size of the hatchling past a certain number of days. If you introduce more heat, the baby will grow faster, that means it will also hatch faster. Less heat, and the baby will grow slower and take longer to hatch. There is some trigger that makes the baby hatch, and I think that the trigger is on a cellular level, they feel like they are at the size they are destined to be (to a certain extent). Their is a signal to the body telling it begin its life outside the calcified prison. Heat increases metabolism. I am attaching a screenshot of a Google search on "how temperature affects cell growth". Feel free to look into it and come up with your own opinion.
I think there might be a sweet spot for incubating all species, there are also temps out of that "Goldylocks Zone" where they can do damage to the cells and growth of the baby, even if its just a few degrees. So maybe at these certain high temps the babies do not reach their full potential because of heat affecting how the cells are growing and the cells are damaged/stunted somehow. That is what I interpret from the last part of the sentence from the google search image I posted.
Sorry for the nerdy rant
