So why can my flyers fly over mountains

… but not over enemy units?

Or am I reading the Battles rules wrong? Page 113 says “[f]lyers can march or hustle through friendly units, and be marched or hustled through by friendly units… Flyers may retreat through any friendly
units, and friendly units may retreat through them.” No mention of moving through/over enemy units, leading me to believe page 19’s “[u]nits cannot normally move through other units” holds .Flyers can (as far as I can tell) simply declare themselves elevated to bypass forests, hills, and cliffs, and are even considered to be high enough up that ranged units can’t target them with normal attacks. But they aren’t high enough up to ignore some spearmen, and have to go around?

If it’s a balance consideration, I get that. But I want it to make sense in the game world, too. And for what it['s worth, I want ranged units to be able to attack flyers, and I want ground units to be slowed down by taking elevation. But maybe that’s just me forcing my preconceived notions onto the engine and mucking it all up. Thanks, Heroscape!

Anyone able to help a poor doofus out?

It was intended simply for simplicity and game balance. It probably ought to be the case that flyers that have declared themselves elevated can fly above other units, realistically.