I have never once made a Sonic OC, despite being the big fan I am. Honestly, when I was younger, I was the kind of kid who imagined myself actually joining in on adventures with my favorite heroes, rather than to make up some avatar to take my place. Hell, that was the basis of my Star Wars adventures that evolved into the RP I'm still writing today; that was when I started making OCs, but characters built around my main character (who is now less of but still essentially an author avatar of myself), none of which with any relation to canon characters. That's how that entire site is; portraying or sharing a direct relationship with a canon character is against the rules anyway.
Mini-autobiography aside, yeah, I've come to realize myself that this is honestly a smart marketing move. They know their fanbase and tons of them are gonna be incredibly excited at this opportunity. And also probably tear it to shreds when they can't make their OCs perfectly but that's another story. It'll probably do well on that alone; I can hear the younger Sonic fans begging their parents for an Xbox One/PS4/Nintendo Switch for Christmas already.