Min speed and drift down VS Mach no.
That may be so, however what we are discussing here is min speed at altitude. The figures are readily available in the book and they are quoted in CAS, as are drift-down speeds. Both are derived from stall speed adjusted for compressibility.
Here is how they derive it on the A330-300.
Min clean = 191kts at 140,000kg below 20,000'
Add 6 kts per 10,000kg above 140,000kg
Add 1 kt per 1000' above 20,000'.
Say 200,000 kg flying at 35,000' min clean would be 191+36+15=242kts
Interestingly, that is how the Airbus FMS also calculates it, and this speed is also the drift down speed one engine out. You will notice that at no time is Mach number considered.