This gets cited here weekly, usually second-hand, so it is worth setting out what it does and does not establish.
Most reported plateaus are not plateaus. Weight is a noisy signal — daily variation of one to two kilograms from glycogen, sodium and gut contents — so a fortnight of flat readings is well inside the noise band. Before concluding anything, look at a rolling weekly average over at least four weeks and at a tape measure, because recomposition shows up in circumference before it shows up in weight. Then track intake honestly for a week: appetite suppression fades unevenly, and intake creeping back up is the single commonest cause.
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.
The narrow version of the question is how to distinguish a genuine plateau from measurement noise and creeping intake, before changing anything. I would rather have one careful answer than five confident ones.
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.