So Sega of Japan are the one who enforces the mandates and Sega of America are reluctant about it. Is there source of information? Would make an interest SWZ topic.
Unfortunately no. It's just from discussion in Facebook group 10 years ago, who got comment from an ex-SEGA saying Sonic Boom was a chance for SEGA of America to have more control over the brand's direction.
I don't think it's up to date with current condition anyway since Ian Flynn has suggested that in recent years, some of mandates have slightly eased up.
For example back then characters cannot change their wardrobes or wear different clothes but right now Sonic and friends wear many different outfits in Sonic Dash, Sonic Sims, Forces Mobile, and Sonic Rumble Party.