That's not what "passive" means. You have to ACTIVEly choose when to toggle the stance on or off. A passive gives the same bonus constantly. ACTIVEly using the stance skills at different moments changes how your character plays. Can you name any other non-stance "passive skills"?
If you can't turn it off, then it's not a passive skill. Active skills have a short term cost (AP, MP, etc). Passive skills have an active cost. In the case of D:OS, the cost is that you can only have one stance at a time.
You can do exactly the same thing in Diablo 3 with their passive skills. The fact that you can toggle it on and off does not make it less of a passive skill. The other part that makes it a passive skill is that you can only have one stance at a time.
First, no, it does not make sense. To learn fire skills, you're already paying a cost: spending ability points into Pyrokinetic. That's the point of having abilities, it signifies that you've learned the fundamentals of said ability.
I thought this was pretty clear, but I'll explain.
For example, imagine you have 5 memory slots, and each spell costs 1 memory. It also costs 1 memory to unlock a skill tree.
So you have the option to specialise:
* 1 point to unlock Fire spells
* You spend the remaining 4 points on Fire spells
If you have to use memory to unlock higher tiers:
* 1 point to unlock Fire spells
* 1 point to unlock tier 2 Fire spells
* 3 points to spend on tier 2 Fire spells.
Or you can multiskill:
* 1 point to unlock Fire spells
* 1 point to unlock Water spells
* 3 points to spend on whichever Fire & Water spells you want.
Combining these two ideas, you might decide to spend:
* 2 points unlocking tier 2 Fire spells
* 1 point unlocking tier 1 Water spells
* 1 point on a tier 2 Fire spell
* 1 point on a tier 1 Water spell
Does it make sense now?
To learn fire skills, you're already paying a cost: spending ability points into Pyrokinetic.
This is incorrect. See below:
One detail that I should stress is that skills are no longer limited by your abilities, e.g. you don't need points in Pyrokinetic to learn Fireball. Instead, you can use any skillbook you manage to find, and experiment with your active skillset on the fly.