The US show has group dances where the judges eliminate people and end up with the best left on the floor alone. They then get points depending on where they were in the leaving order. With 5 dancers thats say 32 34 36 38 40 or 36 37 38 39 40 . You add that to the other dance score.
If there's a group dance and thats whats happening thats another argument for Ali mending her foot this week as you need two good dances.
They are stuck though because if Ali is injured they could find her going next week if she has a bye and doesn't recover or if she dances and survives with the public vote and it gets worse. They already have a case for a roll over week and Ali may need one or make one essential to avoid a one person final. The logical response is roll over.
The problem is if she has a bye she has no votes or marks to roll over and the others start 60+ marks ahead next week.