The way the Debian update process works doesn't make it possible to halt updates immediately. The servers you're getting the updates from aren't controlled by t

The way the Debian update process works doesn't make it possible to halt updates immediately. The servers you're getting the updates from aren't controlled by the Debian project itself, but are operated by third parties. They sync their data from a master machine (which is operated by Debian) 4 times per day. If you're using a mirror that's not under the debian.org domain, there might even be another machine or two in between, each adding some delay. So even if Debian pulled the update immediately, which their archive software isn't really setup to do, it'd take a bit for that to propgate through to the mirrors. If this all seems archaic, keep in mind that all this has been designed 20+ years ago, when bandwidth was quite a bit less abundant.