I actually don’t think the new rule was retroactive; Ryuk was forced by the higher-up to clean up his own mess; hence why he wrote the name himself. I do think it will be implemented going forward though. If the Shinigami king is involved, you know shit has hit the fan. He’s usually very hands-off, so for him to recall someone, yell at them, and institute a new rule means there are probably unforeseen consequences. Still wish there was a loophole for Minoru, like having his mom receive the money. Ryuk could have found a way to deliver a message without interacting, but he’s only ever been in it for the thrill and apples.