See... having you tell me was exactly what I needed... because I was 99.9% certain that long ago, when I wrote CGI for the first time (before I was sucked into the world of Java app servers and crap like that), POST data arrived as soon as Apache got ahold of it. But, here I was, with my newly installed Redhat Linux 8.0 box... and I'll be damned if that didn't work!
It would appear, and I don't actually have any documentation to back this up, but the stock Redhat 8 Apache 2.0.40 with it's bundled mod_cgi is somehow "broken." I am making this bold statement due to the fact that on other boxes where I am either using older Apaches, or even similar apaches which *I* compiled, the behavior was as expected. So, thank you!