Looks like Sega was just fixated on using the word “extreme” with something they were doing. From the cancelled title “Sonic XTreme” on the Sega Saturn, to this, and to Sonic’s “extreme gear” in Sonic  Riders. By god, they were going to use it – and that they did. But, before that, it looks like they had toyed with the idea of just flat out ripping off Tony Hawk. Here are some videos so you can see it in action.
I’m pretty sure it’s just the Sonic Adventure 2 voice clips for Sonic. Personally, I’m glad this game never happened. Because I would of bought it.
I’m Psyguy  and THIS is me putting a hedgehog on a skateboard.
source: TSS