Nice detective work on the Hilton thing. If you think about it, it makes sense. The 850 number was probably picked by the people who created the promo or who are in partner relations specifically to deal with Hilton. They clearly wanted a number that would be high enough to avoid the one spg point transfers by spg plats. The likely had a number around 1,000 in mind, but then revised it down to 850 to permit Hilton transfers, because a requirement above 850 would require 20k Hilton. In other words the 850 number can't be random. It had to be to accomodate 10k Hilton transfers.
But the IT guys would have little reason to know all this history and probably had no idea of the significant difference between 850 and 851 miles so probably weren't paying much attention when they wrote code requiring greater than instead of greater than or equal to 850.