Look closely!! That 12,057# is the GVWR for that 5er! I Can't find a spec on a Crusader for 12,057# closest is the 330MKS at 12,157 and a 10,127# dry weight.
On the Montana the lightest is the 3100RL with a dry weight of 11,705#, it is also 5" taller than the Crusader. So it is interesting that the Ford is faster.
I am thinking something is strange with this test, as my 2001 5.9 Cummins can pull a 6% to 7% grade at 60 mph pulling 11,000# with less than 300 hp. That is at 19,500# GCVW.
If anything the GM and Ram had an advantage, but it all seems a bit off.