Yes I've found this to be accurate. I make sure there's no eggs in other nest boxes before she comes back for that very reason, just saves me from having to move/handle her too much. I've got a few hens that do graft to a particular nest, but some others don't care what nest they're in, or what they're sitting on.
Juggling multiple broodys can be chore, but I like my broodys on their certain eggs mainly for their sit time schedule, this is where I have a block off or 2 ready so no other hens can get on those eggs while she's out with her dailys.