Read the primary source rather than the write-up and the two do not agree, so here is what is actually in it.
Genuine plateaus happen too, and the mechanism is metabolic adaptation plus a smaller body. A body 20kg lighter needs meaningfully fewer calories at rest and less to move, so the deficit that produced the first phase is arithmetically smaller now. The options are the honest ones — increase the deficit slightly, increase activity, or accept the new plateau — and escalating the dose is only one of them.
Where I think it is weakest: the completion rate deserves as much attention as the headline, because a large effect among those who finished is a different claim from a large effect among those enrolled.
What I am trying to establish is how to distinguish a genuine plateau from measurement noise and creeping intake, before changing anything. Happy to be told the question itself is wrong.
Note on sourcing:
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.