I'm so sorry BF

Some patients requiring physical assistance, or step-down care, after acute hospitalizations go to rehab facilities before they go home. A hip replacement is the first thing that comes to my mind as an example, but there are plenty of other reasons.
But many recipients are much more physically healthy post-transplant than when they were before the surgery, and can be discharged home directly and pretty quickly, but everybody is different. I suppose they have to plan for the worst tho.
I think that there is concern that you may have problems understanding and adhering to the strict anti-rejection medication schedule on your own, and that's why they want you to have a caregiver- even if it is BS.

I would talk to your case manager to see if there are any programs that can offer you this kind of service when you leave the hospital... something that goes beyond regular visiting nurse services. There are a lot of great charitable organizations out there, so it couldn't hurt to ask

You are only setting out on this journey, BF. There is still time for the transplant team to get to know you, and hopefully realize that you are capable of handling the surgery and taking care of yourself post-op