Consider the PCM computer only operates at less then 17 Mhz and your P/C is 200 Mhz to 1 Ghz and now you know why.

With that slow of a CPU at higher loads and RPMs the PCM cannot handle all the functions and monitoring thus the RPMS is considered less of a importance and is not updated as quickly as other functions needed for the engine to operate.

If your into shifting close to the limits then install a shift light, use one that uses LEDs since they will light faster then one that uses a bulb and set it to come on a few hundred RPMs lower then rev limiter, thus when it does come on you will be close to the true limiter RPM.