There is nothing magical about this linear relationship; it is an intuitive configuration for pilots, but many other aircraft do not follow it. The requirement makes sense for single-certification, but we must be clear in understanding what is actually happening with this system.

The system counters the hazard of pilots experienced in 'regular' 737s getting close to stalling without realizing, due to lighter stick inputs not having the intended effect. Any MCAS malfunction would direct their attention to this issue.

Actual anti-stall systems (MCAS is not anti-stall, nevermind some shoddy reporting) would still function if a pilot were to approach this flight envelope. This includes cabin alerts, stick shakers, etc.

The scenario where MCAS cuts out, and it's in the envelope of conditions where it actually functions, and the pilots fail to notice this, and the MCAS inputs were needed to avoid approaching a stall, and the pilots fail to correct and avoid the stall .. it's a contrived hypothetical.

MCAS is not a system that activates on a normal flight. Only in relatively extreme circumstances does it even function, and then it only seeks to make intuitive pilot behavior less likely to approach stall conditions. A good pilot monitoring airspeed, trim angle, AoA, etc. will be able to avoid a stall just as well without the system.