@Tim_P_Morris is it 1, 2, or both?!
@Tim_P_Morris thinking a little more about it, the (non-)collapsibility difference probably has to do with the relationship between PH and AFT for the Weibull:
\beta_{PH} = -\gamma \beta_{AFT}
@PausalZ Interesting. Another for my 'I'll never fully understand collapsibility' list.
https://www.jstor.org/stable/26511790#metadata_info_tab_contents
@PausalZ Yes I think that's a helpful point
@PausalZ HR is still noncollapsible and acceleration is collapsible. The explanation was that when you collapse it’s no longer Weibull, and it seemed much clearer with Rhian’s pictures of the compositions.