Five computers are there for redudancy of the computers, not the airspeed system.
On a system level, redundancy is determined by the lowest redundant component. Granted, pitots are dumb with no moving parts, other than heat, however this weak link will be investigated, if it's determined to be a single point failure. Sure, we can say backup is pitch/power, but why let it get even that far.
Carrier pilots are taught to fly AOA for approach.