As a one time certification test pilot, as stated by John Tullamarine to achieve a one knot per second approach rate it was usual to bracket about 0.7 and 1.2 knots per second. The boffins did the correction to 1 knot per second.
The minimum speed after all corrections was the certification stall speed.
The problem with this stall speed determination was that high drag aircraft could have a significantly lower g loading at the stall than low drag aircraft - this could result in a stall speed advantage ie a lower stall speed.
Around the time of A320 certification decisions were made by various authorities to change to Vs1g rather than Minimum Speed in the Stall.
Arguments then arose about the safety factors to be applied. It being obvious that (say) 1.3 Vs was being applied to stall speeds (minimum speed in the stall) which really were not equivalent