Ultrasn0w 1.2.8

Hi there, o.k this may be a strange question but it's necessary for me to ask it! :) I unfortunately was forced to restore to 6.1.3 because of messing up my iphone, but was able to jb with Redsn0w after flashing my phone to ipad bb and then downgrading the baseband to 5.13. I wasn't sure what to do, but the thing is I wound up with 6.1.3 jailbroken, which I wanted. I had previously relied on Ultrasn0w to unlock on 6.1.2, so I took a chance to try the Ultrasn0w on the jb 6.1.3 and it worked. I've had people tell me that isn't possible, but it DID work? How? Anyone know why, was it updated or something? I'd really love to get an answer to I can prove to these people I'm telling the truth, and I am! Thanks Sandy