Is this service a scam?
It’s a scam if they’re trying to sell you a service that you don’t need.
You would be hard pressed to find any of the contributors to this forum say you need this service.
Does a car with less than 20,000 miles and running perfectly need
this service?
No. With the cleaners in today’s gasolines, I doubt you’ll need it at 200K miles either.
Is there any scientific data proving this service extend the
life of the car?
Those selling you the service will likely show you data that looks scientific. I doubt you’ll find it anywhere else.
The real answer for your questions are in your Toyota owner’s manual (not the dealer’s version). Look at the maintenance schedule and if the service isn’t listed in there, you really have to be suspect for what the dealer is pushing.