Well....without a thread of evidence let me try and reason through this.
Difference between CAS and IAS is position error and instrument error.
Due to the large speed range, angle of attack range and altitude range large jet aircraft operate in the error could be significant at times.
It would be a hellacious task to try and use tables or charts to find the correct value.
So electronically fixed and yes, airspeed tape shows CAS.
Found something:
https://www.sciencedirect.com/topics...-data-computer