Actually nvm, take a look at Hoopa's pokedex entries first before saying no raw power was involved:
This troublemaker sends anything and everything to faraway places using its loop, which can warp space
It gathers things it likes and
pushes them through its loop to teleport them to a secret place.
| It is said to be able to seize anything it desires with its six rings and six huge arms. With its power sealed, it is transformed into a much smaller form. |
Hoopa is explicivity stated to actually push things through its rings when gathering them, using its large arms. This should imply some kind of force is being applied when Hoopa uses its rings to transport things, which would even include the legendaries it has gathered.
And heres more evidence of it using force when gathering things it wants:
Hyperspace Hole- Using a hyperspace hole, the user
appears right next to the opponent and
strikes.
Hyperspace Fury- Using
its many arms, the user
unleashes a barrage of attacks that ignore the effects of moves like Protect and Detect
Before this gets game mechanics involved, in simplier terms Hoopa is using its rings to open holes in space time to gather what it wishes and in a likely case, such as pokemon, it even battles them. Hyperspace Hole/Fury are just Hoopas Rings being used in mid battle so theres no reason why they cant be applied here to say Hoopa isnt just using BFR on the legendaries