Here is the language from the TSB:
"Important: When verifying this condition, ensure that the water leak path is due to cracks in the rear sliding window plastic upper rail glass guide, and NOT a leak in the primary urethane seal, between the window and the body; or from the spoiler attachments to the truck cab which are in the same area.
Please indicate power sliding rear window crack in warranty claim verbiage. A leak in the primary urethane seal should be addressed by removing and resealing the window, using the standard service procedure from SI.
R & R the roof rear spoiler and apply seam sealer to the rear sliding window top encapsulate, following the steps in the Service Procedure below."
So, it looks like it does address removing the window if that seal is determined to be the source of the leak. We'll see. As an engineer, whenever you redesign something, it should be tested. How GM didn't catch this when testing the 2019 redesign is amazing and inexcusable.