Not sure if bug or a feature, but summoning units via Satanael active ability does not trigger maximum population block.
As shown on Corsairs - if you have a population of 120 or summoning a unit would exceed that number the active ability is greyed out and inaccessible.
When you use the ability on Satanael, it does not block you from summoning units - in this instance the screenshots are taken in the forge, but it also works during gameplay, I've reached over 300 pop, which has caused some lagging and stability issues. Also super-OP in PvE and rPvE. 2-3 Satanaels are unbeatable.
Reproducability - trigger active ability on Satanael beyond population maximum count (120).