From my experience, my answer is maybe.
They will tell you the reservations have been linked and you can check 3 times before your trip and even do online check in that covers your whole stay. So you think all is good.
Then when you get to the front desk, they have your check-out day something other than what you know it should be. You will produce your linked paperwork and they will be surprised, but they pleasantly type the information into their computer and send you on your way.
On the final night of the first reservation, when you are returning to your room exhausted, your Magic band will not work requiring a trip to the front desk. And actually 4 trips one night.
This has happened so many times I have lost count and I regret buying two use years.
The safest answer is to do the transfer.