andrew_nyc said:

The version of this that has an answer is narrower than the version being asked.

Coming at andrew_nyc’s question from a different direction. Start from the measurement rather than the conclusion. Almost every disagreement here turns out to be two people measuring different things and comparing the numbers anyway.

Adding the numbers, since they settle part of this. Keep the original post as written when you update it, and add the correction underneath. An edited-away mistake is invisible to the next person who makes it.

That is the short version; the long version is somebody else's post.

One thing that is still open after andrew_nyc’s answer:

How people are distinguishing a supplier having a bad batch from a supplier on the way out?

VendorMark said:

Keep the original post as written when you update it, and add the correction underneath.

Careful with the causal language. Two things moving together in a period when five things changed is not a mechanism, and stating it as one makes the thread less useful to somebody reading it later.

Closing the loop on my own question.

Closing the loop. The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.