This is misleading. In 1973 American psychiatrists dropped the homosexuality from the list under the political pressure by the homosexual militants. It was not a scientific process.
I don't see how they could do scientific research in this area. You can't predict which kids will become homosexual in the future, so how do you know that influencing the way they act as kids will save them from homosexuality? I think it works, but developing scientific data to support it would be pretty much impossible.