My impressions and take, those with FAA experience may pick it to pieces.
With respect to the controllers the formal report says,
The controller advised the pilot that radar and radio contact with the flight would likely soon be lost and instructed the pilot to “squawk VFR” (set the helicopter’s transponder code to 1200) and contact the CMA tower once closer to the airport, and the pilot acknowledged
The report even provides the reference as a footnote,
The VFR transponder code of 1200 is used for aircraft that are operating under VFR without ATC radar advisory service (FAA 2019b, 5-2-4). See section 1.5 for more information.
Being told to "SQUAWK VFR" or "SQUAWK 1200" is indication that the radar service being provided is now terminated, it doesn't require the "RADAR SERVICE TERMINATED" call in these circumstances
5-1-13b.Radar service is automatically terminated and the aircraft needs not be advised of termination when: 1. An aircraft cancels its IFR flight plan, except within Class B airspace, Class C airspace, TRSA, or where basic radar service is provided
It seems to me the pilot didn't understand the implications of squawk 1200 in that radar advisories were no longer a provided service.
What is that old rule....."Aviate, Navigate, Communicate"....in that sequence
When you're up to your neck in alligators ignore ATC until you get to the third point of the rule, you might give a "standby", not scrambling about the cockpit looking for the ident button, the old story of "am I up here because you're down there, or are you down there because I'm up here" is relevant. Aircrew at times are cowed by the term "controller".