Yeah, very true on all accounts. I was more thinking spin dash in neutral. It's no doubt a core of his play, but I just don't find Mario's camp game to be strong enough to deal with Sonic's ground speed, since fireballs are pretty easily dealt with at long range as Sonic gets into mid-range where grounded fireballs are more punishable. But I'll defer, since it's not like I play Mario, cancer, or have a cancerous training partner.
It's really annoying that none of my training partners play Diddy, Sheik, ZSS, Sonic, or Fox (well... one does, but it's a semi-generic Fox secondary). Rosa's the closest I get to a top tier training partner, and Rosa is so different from the other top tiers.