

“When properly preheated, the heat is very even” isn’t contradicted to that fact.
Cast iron does indeed suck at heat distribution, which is one of the reasons it needs proper preheating.
But once the pan is properly preheated, then that heat is quite even.
Make sense?

It doesn’t take an hour to preheat cast iron
FTA:
(emphasis mine.) Ovens typically take 10-20 minutes to come up to temperature, and if for whatever reason your oven is already hot, it won’t take longer than what your oven takes to preheat to to get up to temp.
Either way, I typically start preheating as I’m prepping everything else.
And yes, I know I have an even pan because I not-infrequently make omelettes in them.