ثُمَّ وَقَفَ، وَوَقَفَ النَّاسُ مَعَهُ، فَدَعَا.
Translation: Then the imam stands, the people stand with him, and he supplicates.
The particle thumma introduces the next step: Fajr first, then the Muzdalifah standing and supplication. Spending the night there and performing the dawn standing are legally distinct matters.
Wuquf concerns qualifying presence within the prescribed place and time; it does not mean every pilgrim must remain physically upright without interruption.