Nah, it's a general thing from way back that I had to use... worked it out one night when the OS 9.1 updater came out.
Only the US version was available, I had the international 9.04. So after realising I downloaded 60 megs over dialup for nothing... well, yeah. I was gonna use that updater one way or another
...that's how it went.
The updater/installer sees the files and knows you have a valid system to udpate; it knows you're not just trying to get the system for free by updating nothing (you can make a full install from updaters sometimes, if you know what you're doing) because the files are there to start with; then you remove them, so it has no arguments updating these files. Because it's just placing its own, no replacing/checksumming is going on
