Canelo experienced what Floyd did - extreme public pressure to do something. Basically, his badly damaged professional reputation mandated it.
He had to enroll to save face. But it's a sad joke that Clenelo even had the choice to enroll, as other fighters like Povetkin, Stiverne, Ortiz who got popped for PEDs were forced by WBC to do stricter drug testing and they were also fined. Alvarez wasn't fined and doesn't have to do stricter drug testing. WBC is corrupt to the core and they protect Alvarez no matter what.