I think the idea was to tweak the DOB (and personally, my state of residence seems to constantly be in flux, pretty sure it regularly varies just based on how/where I book my ticket). That approach sorta strikes me as viable for backup flights, seeing as you'll clear security with the flight you intend to take which is the one that has all the regular precheck details anyway. OTOH, I've never been stopped when I've had backup flights under the same name/DOB/KTN, though sometimes they'll ask which flight I'm actually on.