You mention stuff that applies to ALL manufacturers (Teslas have rear seats just like everyone else). Then immediately state that it's some sort of conspiracy against Tesla. Persecution complex, much?
The NHTSA is not out to get Tesla. You actually have it backwards. Tesla, and for sure the Teslerati, seems to think they deserve some sort of special treatment. And when they don't get it, they claim it's unfair. Ridiculous.
Also, requiring redundant reminders (audible and visual) is just good UI. Hell, they should insist that seats vibrate, too, just to add a third perceptible form of alert to the UI.
Not everybody who climbs into a vehicle is visually-focused, or aurally-focused, or touch-focused. Having all three methods helps to create a warning that will alert a larger cross-section of vehicle occupants, and hopefully save a few lives.