have read your discussion on what the " books " and what len wrote and advised .
One thing to take into account-- the " pitch " that existed, during that period was much more fwd. than current trends .
The positioning of the body, at the angle used , prior to the late fifties,
had a distinct effect on the flight of progressive movement .

I have known and been to Lens lectures and also lessons ( among many others ) of that era,( also my era ) ,. have been dancing this style for close to sixty yrs ( am a dual fellow and former examiner ) .

I think Len would be mildly amused at the way people parse his words and ideas.
The one thing he always stressed-- technique is fluid, and can and will, sometimes , change with the times .
Much of what has been stated in the past , is opinion, mostly supported by fact .
I tend to agree with Lens theories, and have taught them for many yrs ( including to 2 very high profile past champions, and Amat,s )and still practice the same ideas, by and large, today .

There has always been divided camps, when one makes comparisons with past technicians .
As len emphasised-- the execution of a given sequence is largely dependant on the physical characteristics of the couple in question , You cannot ignore the principles of kinetic energy when applied to motion-- you can, however modify the outcome .

If Len were to see todays exponents, I am pretty much sure of what his major comment would be ( swing dances ) a far too heavy look caused by late release from non supporting leg ( dont even want to think about tango !! )