ryou is fundamentally different from basic coa and it can be used without the black coating, for example kinemon used hardening to push the bird cage, but when he stabbed kaido at the beginning of the raid he only used ryou without blackening it's an invisible armor suit that can be used both offensively and defensively
, even kaido was wondering if they have oden's
ryou.
and kaido is from outside wano, he knows the difference and he had no problem saying that enma is the sword of a strange
haki.
you just gotta pay more attention to details.