Jaime got to choose to be a Blue Beetle. He researched Ted Kord, spent a lot of time trying to figure out what the name meant and how and even whether he wanted to live up to it, and understood from the very beginning that there were expectations around his job and name and, to some extent, what they were. There's a huge difference between *starting* a character as a legacy character and undercutting an original character by back-propagating a false legacy.
Not to mention that it obliterates about half of Perez' run, destroys the entire message of Diana Rockwell Trevor (and thereby seriously dents one of the most valuable parts of the relaunched mythos), and puts Polly's JSA allies in a position of unearned seniority over Diana ("shut up, kid, I played cards with your mother before you were even a twinkle in Athena's eye").