I just checked the first post (which I authored), there was no essay ever written as far as I can tell, I had intended it to become a wiki article.
There should be another thread somewhere that has a long collection of EBT references (pali and agama) to kāya in jhana and 16 APS (anapana) contexts.
At some point I’ll share my notes on this, with detailed pali/english audits. But it’s good for you and others to do your research independently and see if you come to similar to different conclusions.
Here is a new one I found recently: