it's an english tooltip error.

In japanese and in french, the spell specifies that it only extends OUR buffs.

And tbh honest, extending our mana regen is not that big of a deal... especially since we waste it on us instead of using it on a tank/dps. Fair trade imo.

Also, in french it does not say that you can only cast it on someone else. Imo it's more of a bug than a last minute change.