[2021] How will this caster mastery work with repeats?

I saw this among the new masteries on PoeDB, in the 'caster' category:

"Spells cause you to gain Mana equal to their Cost every fifth time you cast them."

How will this interact with repeats granted by spell echo? I couldn't remember whether they count as 'you casting' or not. If they do, this could be pretty good for Archmage builds that use Pledge of Hands + Spell Echo, since it would trigger almost every second cast.