>Automatics have been more efficient than manuals for decades.

No, they haven't. At least, not ones the average consumer could actually buy.

While it's true that modern 8 or 10 speed automatic transmissions do now compete favorably with 6 speed manuals, the former didn't meaningfully exist in passenger cars or trucks until around 2017. Neither did DCTs outside of high-end brands- sure, they're starting to do that now that "torque converter loss" means they don't pass emissions, but that was an option that commanded a premium back in the mid-00s when they were introduced (and still not actually more efficient than a manual outside of shift speed).

An automatic with 4 gears is less efficient than a manual with 5, much less 6 (this was the standard until about 2010 or so); one with 6 gears is likely on par with the 5-speed manual (and loses to a 6-speed, obviously).

So no, "decades" is bullshit. It's a very recent advancement.