That’s not how I ever heard or have seen the term "discrete" used in HEA.
From my reading, and use, "discrete" is an abbreviation of "discrete circuits" which is the antonym of "integrated circuit." From a practical matter this means gain stages are built using individual transistors, rather than chip based op amps.
"Discrete" does not refer to the number of inputs, or to input switching capabilities. In home use, there's almost no need for "discrete inputs" since you only use one at a time.
Very rarely I have read of "discrete outputs" which refers to having multiple outputs which do not share circuitry and may even be isolated by independent voltage regulation stages.
Best,
E