IMO,you're an extremely intelligent person, extremely overthinking things to the point where any mathematical outcome you derive will ultimately prove your theory.
I agree that there is the risk of that. And a much much greater risk that it is perceived that way -g-. So I'll make it simpler:
If you do a post hoc subgrouping then the facts implied by the post hoc-ing had better match up with known reality or it is a bad sign. It is even a bad sign if the implied facts can't be externally confirmed. The discussion between JQ and myself on the relative rate of high MET expression in squamous vs non-squamous is a healthy evaluation of that alignment with reality.
And FWIW, as a followup, the argument I made is just an explanation of one instantiation of the base rate fallacy - or as its close relative is known in these parts, Program Survival Bias. Or, in yet other words, the words of Fleming, any good scientist (or investor) can always find a completely reasonable post hoc MOA explanation.
Finally, care to make a wager? I'll wager that the initially reported OS results of the ARQL nsclc ph iii trial are HR>0.8. I'll even give you 2:1 (although given the site prohibition on wagering anything of value I am not sure what that would mean -g-)