Lol ever developer has a favorite character or writer in comics, take geoff johns, he loves gl probably more than anyone as far as writers go. And loeb really hates superman, always makes him look weaker....
Lol so its not just boon i assure you my newer theory is i think its definitely an alternate universe sub, a new sub zero all together as boon said new characters so this is very possible or one of the previous subs resurrected. My theories.
P.s. I dont think thats raiden posing as sub either lol.