I don't think that is a fair characterization of what I wrote. If the scanning process has a sensitivity of 99.999%, and the next stage in the signal chain has

I don't think that is a fair characterization of what I wrote. If the scanning process has a sensitivity of 99.999%, and the next stage in the signal chain has a sensitivity of 50%, and we consider what happens if the MRI sensitivity drops to 99.9%, that's well in the noise in terms of diagnostic value. Use some of the extra money freed up by doing the MRI 10x faster to pay a radiologist to look at the scan for 10% longer, and perhaps the net accuracy has improved. What is unacceptable about this kind of holistic reasoning about the system? High performing systems are frequently not composed of perfect components.