Not entirely sure why Aery still procs when you spellshield the ability

Because it is a separate effect. The spell you blocked did hit you, but the effect was negated by the spell shield.

HmMMmMMmMmmmmMMmmmMMmmM

Huh

Aery is not based on damage like most cases with spell procs are, Aery is simply done based on hit, which means if a spell targets you, it is guaranteed to proc regardless of spell negation or invulnerability. You can see this with hitting Kayle Ult with a spell, Aery will hit the target.