Why isn't it the same as the blessing before? Well, according to Professor Cantor Eliyahu Schleifer, the minor melody used in the blessing before was originally supposed to evoke the mourners kaddish, since those with a yahrzeit were given priority for an aliyah. The blessing afterwards however starts in major, echoing the major of ya'mod plonit bat almonit l'aliyah harishona, and then at the chatimah returning to the end of the aliyah motif.
Apparently, sometime in the early 20th century, it was felt too complex (perhaps by bnai mitzvah tutors) to teach two different melodies, so the second melody fell in to disuse by them and eventually got "forgotten". But if you'd like a "get out of jail card" with the nusach police, add the melody to your repertoire!
