I wonder what stopping three letter agencies to secretly push for keyboard manufacturers in such way that each keystroke has unique sound and it becomes easier to detect keystrokes.
even if its not, enough decent fidelity data with letter/word frequency analysis paired with small Neural net will quickly disambiguate keystrokes after the first paragraph.
DNA tests used to be in the many thousands of $ range, so they were used for heavy crimes like murders and rape only. Nowadays, it's routine for police to use them for petty crimes like graffiti [1].
It's just the same for camera surveillance, mass exfiltration and analysis of just about the whole Internet's worth of traffic... even searching phones and datamining them is cheap enough these days that US CBP does it for travellers, and German authorities for refugees (until a court order stopped that crap [2]).
[1] https://www.krone.at/2718383
[2] https://www.tagesschau.de/inland/innenpolitik/bamf-handydate...
its like saying, humans haven't reached the moon, even though humanity witnessed it in the sixties.
sometimes peoples memories are short.