I'm sure XP has done enough research and listened to enough user comments to justify whatever changes they've made. I doubt they would have changed one of their preset programs without reason.
I'd assume users have suggested making Large Numbers part of one of the preset programs since this option seems to be popular. Since the General program would be considered the machine's most basic program, it seem logical to make Large Numbers the default in the General program rather than in any other, along with changing it to two-tone, making it an even more 'basic' program.
I could be completely wrong with my reasoning but seems logical to me.