It's the common Renekton build. His W can add multiple stacks.
If you hit with a basic W it adds 2 stacks, if you are empowered it adds 3 procing it solo.
A common trade would be E in >> auto once >> animation cancel with W (basic or empowered) >> Q with PtA boost>> walk through them >> E again with PtA boost
In full on fights, it boosts the damage your ult AOE is dealing the entire time and any more casts you put onto them.
It's a preference thing between PtA and Grasp, I grew to like PtA but I'm willing to revert back tbh.