So if I assign a devotion ability a summon...

does it get the benefit of my +pet stats when it procs? I know my pet will proc it on attack, but is it actually using my pets super boosted stats for damage and such?

I believe so. why wouldn’t it?

edit:
sidenote, if the devotion allows for the pet in the devotion calc of grim calc https://grimcalc.com/Mastery/Occultist then the skills that will proc it is also listed(sometimes the pet skills are listed, without the pet, so thats meaningless and can be ignored)

From the Game Guide:

Celestial Powers
[…] Note that when you assign a Celestial Power to a Pet Summon skill, the power will be triggered by your pet instead of you and will scale with any bonuses that normally affect your pets. […]