Who started the nonsense of HASELL before steep turns?
Mostly the authors of practically all UK flying training manuals who were ex air force pilots and instructors such as, Phillips, & Cole, Birch & Bramson and Ron Campbell-Oh and also that nice man that produced the latest EASA masterpiece you love, Mr Pratt:
I quote from his book - AFE- The Private Pilot Licence Course-Exercise 15 (bottom of the page)
HASELL
It is usual to carry out HASELL or HELL checks before starting a steep turn
If you ever start instructing again you might want to read that book as its the largest selling UK flying training book.
Meanwhile the first book on flying training after the war, and I know you will be familiar with this one says:
Birch & Bramson - FLIGHT BRIEFING FOR PILOTS Vol 1(5th edition)
Page 227
Ex 15 Advanced Turning
PRE FLIGHT BRIEFING
AIRMANSHIP
Height
Airframe
Security
Engine
Location
Lookout
Suitability of weather
I do commend you on the use of the word emphatic though, its one of my favourites, along with arrogance and ignorance!