I don't think it is good advise ...
to tell new sailors that when healing becomes excessive, just release the main and let go of the tiller (or wheel). That just lets the boom fly, the boat changes direction dramatically, sometimes swinging through the wind so that the jib backwinds while cleated in and causing even bigger problems. Sure, the boat momentarily stands up (too abruptly). But, my general feeling is that simply releasing the mainsail can cause more chaos than wanted and gives everyone even less confidence.
Of course, you want to ease the sheet or preferably the traveler, but it should be controlled. I found that the best way to ease the concerns of any crew who are nervous about healing, is to have them steer. I instruct them to maintain the course and I play the traveler and the sheet to demonstrate how healing is easily controlled. Normally, we are dealing with people who are nervous but rational, whose concerns can be tempered by a confident captain. Of course there are people who have an irrational fear, and I am sure that is a bigger problem.
I will also concede that nervous people on our boat are comforted because we are on a small lake with a lot of boats around and warm water. People basically understand that even ending up in the water is not a big deal where we are. It is something entirely different, though, for a nervous person to be miles from land in even a moderate swell, no boats around, and frigid water. Psychologically, people know that being in the water in those conditions would be a major crisis. So if you can get over the hurdle of instilling confidence under controlled, benign situations, rather than waiting until you are miles from shore in arctic waters before the person first experiences a healing sail boat, you will be better off.