No, as terraforming means changing that.
Whether it is really possible, is a different question, but after you have an atmosphere, you could have engineered microorganism processing the soil etc.
In that sense then the term "terraforming" is on equal footing with alchemy.
Just exposing the Martian soil to water for some time is enough to destroy the perchlorates.
(Turns out there's a region in Antarctic with them too, so we can always test things there.)