Energy transfer is also a function of mass. The TAS/IAS you have to wash off is a function of how much above Min Drag (or whatever it is called in the particular aeroplane) before you start into the low speed regime.
Level flight followed by the trend vector on the PFD the same length as 10 knots seems to work without having to do a climb. It does not compromise the test point.
Start fast and then climb above the level flight altitude (particularly if you are near to max altitude for the weight/config/CG) to start a '1 knot per second' decel obviously works for that programme but that is judgement decision.