Multi-sensor inputs are not required for systems whose failure impact isn't rated as catastrophic, which Boeing specifically avoided in their safety analysis, ostensibly due to the fact they knew the FAA would require sim training for a multi-sensor system. So if you accept Boeing's original classification it is not a defect.
Given that upon further testing after these disasters, the results required them to reclassify MCAS and the Flight computer it runs on as a single, potentially catastrophic point of failure, it is now a defect.
Just wanted to point out that regulationwise, that situation evolved over time due to withholding or material omission of critical information with regards to the nature of the system to regulators.
Whether or not a jury will agree is yet to be seen.
