This is a pretty clear example of overthinking a problem...
The vehicle is covered by powertrain warranty for 6 years or 60,000 miles. Go to the dealer and say your engine is acting weird, and explain the problem. Explain you would like it fixed as your powertrain warranty hasn't expired. I would be amazed, if the dealership did anything other than just fixing the vehicle.
Don't bring up TSB, don't bring up that you think it should be covered, play dumb and wait for it to be fixed. It's pretty clear that a throttle body is part of the powertrain, and the dealership can probably push this repair through. If you starting bringing up the TSB and how it may not be covered but you think it should you are creating more work for yourself up front.