I say this because look at traditional astral travel.
If you are doing it the “right way” which is very mana intensive the following happens:
1) The astral traveler’s spirit leaves it’s body on it’s home plane and wanders the astral plane as a spirit.
2) When it gets to the plane it wants to be on, (assuming it’s the case), it creates a body on that plane (via one of several mechanisms)
3) It then animates that body. There is then a silver cord going between the two bodies and spirit hops between them.
If the traveler with two bodies is on the astral plane, he/she/it will have two silver cords (or three)
4) However, this is tricky to do as it’s very expensive and both bodies need to be kept safe and fed, bathed, relieved etc.
The unoccupied body, in other words appears to be a sleep or in a coma. It will die if not cared for.
Tom was out on the astral plane with his body in a coma. The wizards had to sever the silver cord, otherwise Tom could have eventually escaped back to earth and just stay there and it would have been very hard/expensive to get him back/off of earth (even if they knew that’s where he was)
Remember the comment about “he’s got a body stashed out there somewhere!” They knew Tom had a body somewhere, so they had to sever his ties to it in order to truly bind him.
So yes, what you are saying is definitely possible and in some cases being done.