Gavra, I don’t know what form of FDA supervision R’ Moshe was referring to. It seems that the Nirbater Rov feels that that supervision is no longer in effect. Which leads to my response to JT: I am understanding that the Nirbater Rov is addressing the possibility that the availability and fear of chemical testing would replace the need for human supervision which existed at the time Rav Moshe was mattir, but no longer does exist. He is saying, though, that it does not create a mirsus – because they don’t have any policy to do it, and the only available test is DNA testing, which is expensive.
Again, I don’t personally know what the metzius was, or is now, but the OU itself acknowledges that it did change, although as noted, they say for the better.