Well, except that is Cass's perception of the Batcode. It's, in fact, what Cass needed the Batcode to be, because Cass was all about self-castigation. She doesn't want to be forgiven, can't believe that what she's done will ever be okay. (Hence her respecting Bruce, who's an ass to her and wants her to be more devoted and broken, more than she respects Babs, who forgives her and wants her to be happy.)
So, of course, since that's how she interprets the Batcode, she'll fail to see or properly understand those examples that she sees of the other Bats not acting that way (... not that she'd have seen many, because again, Bruce was never interested in including her in anything but violence). Thus, she'd have to see it in someone who wasn't a Bat, and have to see it work fully and completely (as, by meta-necessity, it never can for the Bats), in order to finally understand it as a legitimate thing. Makes sense to me.