PM- I have continued alittle bit ofmy own research and many Rishonim agree with this tosefos. See Rosh, see hagohas maimonis (YOm tov Perek 4,mishna3). It is not clear from the rambam what his view is on this as he does nto give a reason for the issur of taking some oil from a candle.I have not had time to look at the Tur and others.
This matter is obviously extensive and it is not at all clear cut that this is not gram kibbui (see gavra at work one entry earlier).
i am indebted to gavra at work for his pointing out that R’Moshe himself may have considered shutting off gas a gram kibbui.