Beardy you beat me to it! Your responce to Fireflybob is correct, form drag is in relation to speed and high speed at low level has much more effect than at altitude due to relative air density. With regard to the policy that some have of trying to slow down early when above the profile in order to get the gear/flaps out to help recover the plot this technique simply does not work best. It might make you feel better to have low speed but in terms of losing energy from the system the most efficient method is to maintain high speed with full speedbrake and go down first ( high speed, full speedbrake, dense air = lots of drag ) then slow down second. Have a think also about the go-around situation. If you really are too hot and high and have to give it away, which would you rather, a go-around from low airspeed with high rate of descent or one from level flight with high speed. Answers on a post card! As a further thought on this, using the low speed technique how do you know if you are going to be stabilised in time by 500’ AAL? Its very difficult. However using the high speed method its simple. You descend through the profile ( below the glide ) level off with idle power and let the speed decay if you intercept the profile again before the speed is back you need to make another plan!
To sum this all up imposing a rigid ‘250 below 10’ SOP does not make things easier for the pilot. Quite the reverse it removes a useful tool which can help us efficiently manage our descent profile. It is like banning the use of speedbrake to make our lives more difficult. Thus the argument re. training/low experience does not hold up. Indeed most JMC Trainers wish to see a change to this SOP. For those who quote the USA at us, those who have operated large aircraft both there and in Europe will know that ATC environment is very different with fare less segregation of fast/slow traffic in the US hence a blanket ban on high speed makes more sence.