Player buffs from Spriggans do not stack with multiple Spriggans - bug?

It appears the buffs to the player granted by Spriggans do not stack, and I cannot see why, beyond this being a bug. Am I missing some mechanic here?

Note: Easily tested, with 4 points in Spriggan’s Aura of Retribution. Note your crit chance. Summon first Spriggan and your crit chance will increase by +8%. Transform into Spriggan Form yourself to summon the 2nd Spriggan. Your crit chance will not increase further. I assume the same will be the case with its Spell Damage buff too.

It’s not a bug. It’s because it’s the same aura. Same thing if you have 2 paladins with Holy Aura. They won’t stack. But you will benefit fromall the different nodes taken. Ie if one paladin takes fire pen and the other takes ward retention you will have both but the base ele res is not double.