A claim built entirely on a subgroup analysis — what changed since

On the subject in the title: A claim built entirely on a subgroup analysis — what changed since Working notes rather than a conclusion.

I have seen PIONEER 6 (N Engl J Med, 2019) cited in support of a claim I do not think it supports, twice this month, so I would like to work through what it actually shows.

My reading is that the trial is sound for its own question and is being stretched to answer a different one. I might be wrong about that, which is why this is a topic rather than a correction.

What I would like from this discussion: someone who disagrees with me to say why, with the section of the paper they are relying on.

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

post #2 is right about the mechanism and I think understates the practical bit.

Bias towards the null and bias away from the null: different criticisms have different directions. Differential dropout might bias away from null; conservative statistical analysis might bias toward null.