when a brake hose goes the inside lyre of the hose delaminates and shuts the back flow of brake fluid off and holds pressure on the caliper if that makes sense if not someone will explain it better.
That's about all there is to it. The inner lining of the hose can collapse and restrict flow back to the master cylinder, which can hold the brakes on. Especially true if the hoses have been clamped with vise grips for the caliper swap process. I've seen brand new hoses ruined like that, it's a lousy habit to get into. Plug the hole or catch the brake fluid. From the outside the hoses can look ok too, the brakes dragging or locking up is usually the only symptom.
The other thing is that it really takes the disk spinning at speed to knock the pads back. If you step on the brakes and just turn the wheels by hand with it up on stands I would expect them to drag a lot longer before the pads get knocked back, with the car rolling it only takes a second. The wheel bearing end play can make a difference there too. But there were old school drag racers back in the day that would switch disk cars to drums because of the pad drag. Can't imagine there's much to be gained there though.