Rescue Swimmers are good for persons in the water or trapped underwater, in caves etc but free dropping to swim to a vessel seems utterly pointless.
Winchman can be put in the water, on a deck, on a mountainside, into a building and immediately has control of the casualty and is able to assess their medical needs and treat in situ if required. We rescued someone from 8' breaking surf recently where a swimmer would have been unable to extract the casualty but the winchman attached to the wire was able to place a strop and quickly effect a rescue.
In the prog I watched that triggered the question, that's what happened. Plus they were unhappy winching directly from a yacht due to the mast & rigging, so the swimmer dropped into the water and got the crew to jump in with him for the basket. Seemed as bit odd to me, but as I said, I've no experience at all of such things.