Depends on your version of software. If you go DCT TO a WPT and select ABEAM WPTS, the software deletes the temperature/temp line in the WPT data page. I have seen that screw up climb forecasts/CRZ availability. Blockpoint 14 supposedly fixes that.
And then you are honking along at M.856. Speed is life, but that drastically affects fuel consumption. The step function
AFAIK, assumes ECON CLB/CRZ values.
Two possible reasons.