No this isn’t the infamous Sonic Xtreme originally developed for the SEGA Saturn but cancelled due to development hell. Sonic Extreme was a cancelled skateboarding game originally pitched by a development studio called Vision Scope Interactive, which as the name suggested involved Sonic characters preforming skateboarding tricks and races similar to the famous Tony Hawk Pro Skater series involving hover boards. A prototype of the game was originally found in a Xbox devkit and leaked on the internet in 2011.
Liam Robertson, a known contributor to the website Unseen64 that specializes in beta and cancelled video games, decided to investigate further into how the game was originally pitched by contacting Vision Scope Interactive employees. The results includes how the opportunity came to be due to helping with developing the CG cutscenes in Sonic Heroes, how the prototype was quickly assembled and pitched, and it’s connection to the similar Sonic Riders released years later.
What Sonic Extreme might have been if it became a full title is unknown, but it’s nice to know more information about another curious case in Sonic’s history.