I've always suspected that, given Sabrina's severe appearance due to her encounter with the werewolf, DC & Company probably didn't want Lisa Richards to be seen as, for lack of a better term, "normal" until Sabrina had her makeover during Leviathans. They wanted the image of Lisa Richards as the shattered Sabrina to remain uppermost in our minds and for nothing to change that, which her playing a character in 1897 possibly would have.