It seems to me that your statement has some assumptions that may not be true, that a MCAS failure caused runaway trim would be recognized as such by the pilots. The ultimate issue may be a runaway trim, but a MCAS failure may not produce the normal indicators that would lead the pilots to diagnose the failure correctly within the time available. Assuming that a MCAS failure is the same thing as a runaway trim failure and should have been handled by the pilots, while technically correct, might not be an appropriate conclusion.