I think the author was referring to processors handling UI displays rather than a computer system that has only the processing power to only handle a blinking LED.

For example if a UI display showed:

"Warning: MCAS overriding pitch up. Disable?"

Is better than a LED #234 and LED 412 are on. Consult manual for instructions.

I would imagine that a lot of the fly by wire or control systems nowadays are either analog systems or very very simple digital systems (with extreme redundancy).