I thank cherybim for the posting and I certainly am respectful of PM’s knowledge. Allow me to interject a possible compromise here. The gemoro ,at times, says, “halocho ve’ein morin ken”. It is the halocho but you don’t publicize the psak-for whatever reason it may be.
I have to take cherrybim and others (oomis,gavra at work) at their word that this is what they heard from R’Moshe zz’l and his many followers. On the other hand, PM is ceertainly right that in his WRITTEN teshuvos, R’Moshe zz’l doesn’t differentiate between lowering the gas or turning off completely (see excerpt in the teshuvo mentioned). I can only assume that R’Moshe zz’l did think it was muttor and allowed some of his talmidim to pasken accordingly. Nonetheless, on the larger point of giving a blanket hetter, he demurred, so as not to go against the minhag hamokem.
And R’Moshe zz’l did this many times. I clearly remember him writing a similar Psak on artificial insemination when he writes that it is muttor but that it is not to be publicized. Yes, I know, once the teshuvos were written, it became publc but chek out the teshuvos and you will see that when he wrote this, he meant it only for the people to whom he addressed the teshuvo.
So, oomis is right in saying that this was the minhag on the lower east side (I imagine0 but PM has many written teshuvos on his side. All in all, this has been a wonderful posting-true “milchamto shel torah’.