The Lilim for light flat out didn't exist until the reprint. If you looked over the list of SSR eidolons prior to the reprint, the fact that there was a Lilim for every element but light (even illusion has one!) was something that stuck out. Now, it's a matter of noticing how far down the light Lilim is in the list, remember that the list is sorted chronologically by default, and that Pride is actually the first union type event.