He may well be one of the “humanized” Klingons from the Augment virus, who is using prostheses to look like uninfected Klingons. Or who had less-than-successful plastic surgery for the same reason. But didn’t yet modify the human style teeth.

At this point in the timeline there’s probably a mix of original ridged Klingons, TOS-type humanized Klingons, surgically and prostheses-restored Klingons, and overreacted-gene-therapy blue/grey double-nostrilled Discovery-style Klingons running around. Probably on separate ships so they don’t have to look at or be looked at by other style Klingons who consider each other dishonored.