Calculate Alpha number for every 2nd overlap

Hi Pieter, can you help me confirm that I'm not crazy.
I believe that pasting the reprex provided by ron4, doesn't produce ron4's claimed output in a fresh session.
i.e. the z values are not all -1.232498, but rather NA (and for reasons I originally discussed with ron4 when I provided the code he has shared as his reprex... link
Or am I missing something?