Seems like there is a bit of confusion here.
The Gemara does not invent a new heter of cholov yisroel. It simply forbids chalav akum. Thus, anything which does not fall in that category, such as CY and, as Reb Moshe held, Chalav Stam is permitted medina d’gemara. This is because we can rely on the companies and the supervising agencies to ensure that the milk is from cows.
Reb Moshe writes that although Chalav Stam is not chalav akum, and thus 100% mutar, there is still room for one who is a baal nefesh to be machmir and require a Jew to supervise the milking. This cannot be due to the unreliability of the companies and the supervising government agencies, for then Reb Moshe could not have permitted it. It is safe to conclude that relying on these parties is a 100% valid fulfillment of Chazal’s guidelines. The reason for this possible chumra, which again is only for ‘baalei nefesh’ (not those who want to be baalei nefesh) must be in order to actually be proactive in making your milk kosher, and not becoming kosher by default.
Now, if one actually has a rav that he/she consults on a regular basis, there would be no need for them to guide their life based on postings in the CR. So the audience here looking for guidance must be from the majority of people that pasken their own shailos and rely on the ever popular Reb Alle (alle teeyen azoy, alle feerin azoy, etc.). Being that the question here is one of a d’rabannan, and there are those that permit and those that prohibit, one may rely on the more lenient opinion based on the rule that safek d’rabanna lekula.
One who has a rav, and was told that CS is permitted is otherwise, must follow the psak that they received.
For one to decide that he is enough of a baal nefesh to be machmir on Reb Moshe’s chumra, he must do some serious self analysis whether he is being truthful and honest with yourself.
One final point. Despite the abundance of Cholov Yisroel, the current price of a gallon of CS milk is approximately half that of Cholov Yisroel. So what Reb Moshe wrote to the school that it is worthwhile to teach the students a concept of being machmir, since the price difference is only very slight – seemingly does not apply to today’s market prices.
Now, let me get back to my white milk chocolate KitKats…..