It's gotten a lot better since we entered the KindleBreak era. The community went nuclear, and now instead of applying various hacks to try and prevent updates from being downloaded, the jailbreak package includes a little service that (as I understand it) watches the disk and immediately deletes anything that looks like an update package. The MobileRead "Open Sesame!" thread [0] has all the modern tooling in one place, if you're interested.
[0] https://www.mobileread.com/forums/showthread.php?t=320564