Could be a burble tune. Some tuners modify the fuel tables to stay rich for a little bit after shifting. Nothing bad really unless you're running a catted setup or don't mind changing injectors at every 30k.
I gotta say a stick STI for it's price...not worth it...my good friend had 2019 an I drove it a lot an wasn't impressed at all...yet still fun to drive an all. Now if u have the money..... definitely put some into it an make it sound like this then that's a different story cuz God damn that bish sound good! I fuckin love how these cars sound. By far one of the best sounding cars ever!!!!