One important aspect regarding hydration is that, as I mentioned before, it takes a lot of energy to turn water into steam. Whenever you add water to dough without increasing the heat, theoretically, you're slowing down the reaction (to an extent) and potentially creating less spring. The only way to judge the impact of hydration fairly is to, as you incrementally add water, you should be adding a proportional amount of heat.
In essence, the hydration test wasn't really the LHLT vs. HHLT or HHHT vs HHHT, but, rather, it was the LHLT vs HHHT comparison.
Temperature is somewhat independent. Generally speaking, you can increase the temp and the oven spring will increase accordingly. Hydration, though, is completely dependent on heat. It's not just about adding water to the equation, but about adding steam. Steam is your star player- and to produce more steam, you have to add both water and heat.
For every temperature a pizza can be baked at, there's going to be a max hydration sweet spot, where the dough doesn't burn, but enough heat is transferred to convert all that water into steam in the quickest manner possible. Assuming, of course, oven spring is your goal.
Thickness factor (as I've mentioned before), heat and hydration. You're just boiling water using the measured combination of these three components to produce the most steam in the shortest amount of time. This is why all the legendary Neo-NY/Elite pizzas are very thin, relatively high hydration (balanced, of course for, crispiness) and baked in hot, thermally massive ovens. Street style works the same way, but at a slightly lower temp.