New sports cars are starting to come with digital bc a needle on tach cant read fast enough to keep up with the engine speed so those don't necessarily read true either.
I have used all types of tachometers and gauges on bikes when doing field testing. A digital instrument (tach) requires too much concentration when you mind and eyes need to be gathering more important information when riding at high speeds. An analogue instrument is much easier to watch out of your peripheral vision without having to take your eyes off of riding and focus on the 3 to 5 digit number long enough for your mind to take a snap shot of the number and remember the number.
The human mind functions in more of an analogue fashion (an approximate number is usually good enough). We use to glance at a clock and say its about twelve fifteen and that was close enough to the correct time to satisfy the need to know what time it was when you arrived somewhere. Now with all of the digital clocks and phones, we have to take a little more time to focus on the number and remember it was exactly 12:13 , or 12:16 or whatever the number was, but it still was about twelve fifteen if someone ask what time you arrived.
Dash instruments are there to let you know approximately what the engine RPM is, or the approximate oil pressure or the approximate engine temperature, etc, etc.... It really does not matter if your engine RPM is 200 RPM off. It really does not matter if your oil pressure is 10 psi off from the National Bureau of Standards as long as your instrument readings are repeatable
If you need exact numbers for testing purposes you are best off using a data recorder and not risk misreading or forgetting the critical test data.
Most OEM tachometers are not accurate and not responsive enough to use for meaningful testing. The RPM readings on the OEM R6 Yamaha tachs typically read 500 to 1000 RPM high. The RPM reading on the OEM GSXR 1000s tachs typically read around 800 to 1000 high. The majority of the OEM speedometers are set to read 4 to 5 % high.