SFC (specific fuel consumption) is less at higher altitude than at sea level because the ratio between air and fuel is in weight, that means that less denser air, less fuel required (true for all endothermic engines).
Hawk37, 1.32 is Best range speed only for jet a/c not for turboprop (turboprop best range and best endurance coincide with Vimd), because the difference is in the curve of power/thrust required, in jet engine tangent to the total drag curve at 1.32 Vimd.
The example you give is totally wrong, Vimd is a KIAS speed, nothing to do with Mno, (we use Mn at high altitudes for Mcrit limits) and doesn't change with altitude (effects of compressibility starts at speed above 300 IAS, so can be trascurable on this matter). Obviously the Mno counts, but only if it is limiting, pretty much impossible, maximum Mno have always a sensible margin above maximum range, that is even lower than long range speed.
Vmd and Vimd are both correct terms.
FB