Re: theory on cardio endurance & muscular endurance
the muscles/CNS and metabolic pathways function a bit differently from each other.
1. heavy weighted pullups + endurance pullups = high endurance potential (more muscle) + realizing that potential with endurance work. High strength tends to lend to "endurance" at lower weights obviously enough.
2. Metabolically, high intensity work especially longer than a couple minutes in duration strongly depletes glycogen pathways and strongly taxes oxidative.
This is the reason why you can run longer at low intensity when you do HIIT. Not because of the strength increases and fast twitch fibers.... fast twitch tire quickly anyway. Sure, they make some difference, but the vast majority of the improvement is metabolically, not muscular/CNS-wise.
These are definitely not the same thing. Don't confuse them.
CNS + muscular versus cardio (O2 blood flow) + muscle metabolic endurance
P.S. They are similar in some respects as you noted, but different in others as I tried to explain in how they work.