While keeping track of USNs for the Stack Clash vulnerability, I noticed that already published USNs were showing up before ones published later. USNs 33{24..27}-1 were originally published on the 19th, and now they show a date of 21st (compare the webpage with the mailing list post for 3324-1). For 3324-1, it seems some kernel packages were dropped from the list. However, it is tedious to examine all the updated USNs manually.
Is there a place where I can see what changed in a USN?
Aside: why would they update an USN, instead of posting a new one and incrementing the number after the hyphen?