As I recall, not all were .. but some were. I bought my xbox right around that time, but I didn't get the Halo one... I got a holiday bundle of the xbox Pro and I got a Falcon. At the time there were a lot of threads reporting Falcon sitings and I seem to recall reading some people reporting that their Halo version xbox was a Falcon and others reporting that theirs was not.
edit: I don't have a link so you'll have to search, but there is an easy test to see if an xbox is a falcon, assuming you have access to the xbox in question.... you can look through one of the vents and see some inductors there. If there are 3 of them, you have the old style. IF there are 2 of them (and then just an empty spot on the board where a 3rd one would have gone) then you have a Falcon. If you search there are plenty of pictures out there.
Of course you have to have access to the box for that.