Ionic Spark Dealing Damage Against Not Transformed Shapeshifter Autos?

I just played a game of TFT where someone had an Ionic Spark on one of their champions and it kept going off against my Gnar for auto attacking without transforming. Being Gnar and a shapeshifter, I would think that would happen after transforming but this kept going on every auto before. This also happened near the end of the match against my Jayce and Nidalee, both auto attacking without transforming but still taking Ionic Spark damage. There isn't recording from what I tried finding of it and I don't know if anyone else has ran into the same issue.