Sideslipper,
You could always give BZN ATC a ring, I am sure they would love to enlighten you as to why they said what they did. Maybe you have found an error in a document (it happens all the time, someone somewhere misses a reference and a document slips through the net)
At the end of the day, the RAF have only been doing this since 1918, as opposed to civil ATC which started in the late 40's early 50's.
Just because it is different, doesn't mean it is wrong!