The FDA announcement make no statement in one way or an other about the cause, only that there is a problem with two monitor sensors under certain model numbers and serial numbers. It not a given that a single production batch include a multiple of model numbers and products. Assuming it is bad quality control of the chemistry is thus not supported by the FDA announcement.

It could be the software freedom conservancy assumed software bugs, with the same limited knowledge as the assumption being made here about chemistry quality control, so readers will have to decide which sounds more likely. The article do state later that "We also will probably never know whether this issue was in hardware or software... the public deserves to know the technical details ". We can make a favorable interpretation here that they acknowledge the possibility of it being software, hardware or QC. Making accident reports public information is a common step in other areas in order to allow people to learn from mistakes and produce better products.

I will add that blaming faults on human error has generally been shown to be a dangerous route when dealing with fatal accidents in all human endeavors. Correct training and behavior by patients can help to reduce fatal accidents, but one should always be careful to put blame here as a culture of blame generally produce more rather than less fatal accidents. Human-computer interaction is a complex subject and its very possible that the accident rate of those specific CGMs could have been reduced or prevented with better design, depending on what the issue actually was.