Having read the article, it looks like another "
BOLS Bridge Tip", and quite a reasonable one.
But the tip is "over a 6-level save, pass asks for first round control [in their suit]."
So it's not really explaining "why it has to be, theoretically", more stating "this is the obvious thing partner would not know when considering bidding 'one more', so agree with partner that this is what [the forcing] pass asks for." May not work all the time, but any agreement is better than no agreement, and this one is probably the best (easy) agreement.
The fact that duffers like me can work the reasoning out from first principles simply shows how obvious it should be. Not "is", absent actual agreement, mind you.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)