I would suggest that it might depend, "right speed for the job" , I use TTS(text to speech" all the time with a large speed, regular people will not understand

I would suggest that it might depend, "right speed for the job" , I use TTS(text to speech" all the time with a large speed, regular people will not understand what it is spoken but for me is fine, I can read a news article like this one without no downsides versus someone that uses his eyes and reads at normal speed or someone that listens the TTS at regular speed and with some natural sounding voice. What if the 1X is a limitation of our vocals, we could maybe lose our air if we would speak much faster, if someone would like to do some sicence on this I suggest finding people with disabilities that use TTS technology and try to get some numbers. I personally don't use faster speed for the reason to listen to twice as mch content but probably to finish it faster. I listen/watch youtube at regular speed since I use this videos for entertaining and I did not consider to speed them up, though for audio books the app had a big speed button so I used it mostly at 1.5X