That sounds right.

I suppose the difference seen with NT 5+ vs. 9X could be the actions
NotePad takes in each case. I suspect the newer versions write over
the existing file while older NotePads write a new file (replacing
the original).

This could be an issue for any application that updates a file in
place and then relies upon the EOF setting in any important way.
Some have theorized that the problems (or at least some of them) with
PST file handling could be due to this behavior of the NAS device.

Perhaps SysInternals' FileMon or a similar utility might shed more
light on this.