Yo Yo
The idea of offloading the stab by releasing elevator input began when jet upsets began to be better understood.
At the very high speeds reached, the stab could not be trimmed while max elevator input was being applied. I believe it was a group including Boeing and Airbus who issued the advice (no particular aircraft in focus) to release elevator pull and trim (gently) the stab before applying elevator input again.
Of course in the case of an upset the procedure was not expected to be applied at treetop height but further up.