Wow, you have a really good eye! My edition has that alteration too. o.o
I notice they tend to change seemingly meaningless details like that, in most of the volumes. Like, in volume 13 when Syaoran first sees the library, he originally said 'Toshokan?'(a library?). In the manga, it was changed to say 'Koko wa?'(This is?).
Maybe it's a game they're playing with those who buy it weekly? ;3