My email to my dad apparently went astray, but I finally got an answer. He wrote:
So it seems like my dad's agreeing with the mission president who indicated that helping out with this type of thing was not unusual in the least. If the mission president himself had tried to persuade Langi to switch from the U to the Y, then I can see a problem. But I don't see any issue at all with the mission president helping out with some legwork once Langi told him he wanted to transfer, just as he would have done with any non-football playing missionaries who needed help. As my dad said, the missionaries themselves are not able to do that type of thing, given their strict correspondence rules.
This jives with my experience and those I have spoken with.