Looking this up, it appears TSS is based on total elapsed time of the .FIT file and what you have displayed on your Garmin is irrelevant. Which I suppose is why Coach’s instructions are to turn the Garmin off entirely for any lunch-length ride pauses and why he’s never commented one way or the other on the use of autopause otherwise.
This does not address Seattle’s 200 stoplight paradigm but that’s not a scenario that applies to me so not of huge relevance for my situation.