Question about the passive skill Preparation (Mage)

[Duminant2021]

In the passive tree of the Mage there is the Preparation skill, which increases the next spell every 3 sec.

The question is how it works if one spell is duplicated. For example, with the Overcharge node (a chance to duplicate Blast) in the Lightning blast or Stormbringer in Surge (4 lightning bolts for 1 cast at once).
Will it work for all spells, or only one spell in all cases?

P.S.
I read an already closed topic, where they discussed the effectiveness of this skill.

Mage's Preparation node needs a rework

I think it would be easier to time if it were every X spells cast, rather than every X seconds, it would also benefit faster casting skills more though IMO it should probably have a modifier that makes it benefit slower/more expensive skills more than faster/cheaper spells (though the former tend to do more damage so it’s probably not an issue).

And a proposal arose.
It might be worth changing this skill to a guaranteed critical hit chance trail of the spell.
1 pumping every 13 sec.
10 pumping every 3 sec.
Naturally, the numbers are conditional.
What do you think ? Crete is useful at all stages of the game, and the presence of a temporary CD will not allow him to be abused by too DPS skills.
But it will allow it to be used in assemblies for strong, but rare castes.

[Llama8]

It should work for Overcharge (since you’re casting the spell which then duplicates itself) but I’m not sure about proc’d spells since you’re not directly casting them yourself.