Dear Neville,
To my knowledge pikuach hamamshala was in place for chalav yisroel Before Rav Moshe’s teshuva. It seems that was understood in his teshuva about the milk of a mechallel shabbos. Which was before the first teshuva about chalav hacompanies.
See the top paragraph on the left column.
https://hebrewbooks.org/pdfpager.aspx?req=917&st=&pgnum=80