A way to verify this would be to look for attendee lists from early
POSIX meetings, though I'm having trouble locating them.
I was the original editor (more in a minute), and I believe I have an early draft on my Masscomp machine, which is currently not powered up.
I'll try to add it to my to-do list to bring this online. The first section has an attendee list.
I also have (in a box in my attic) some of the original handouts, including minutes. That is already on my to-do list.
My initial search turned up this document, a 1995 retrospective from Hal
Jespersen, where he credits Stallman for coining the name "POSIX":
https://dl.acm.org/doi/pdf/10.1145/210308.210313.
I just read it. Much is correct, but that document has numerous errors, including the transition from /usr/group to IEEE (which Heinz and I were involved in - Hal was not). I'll send a number of updates/corrections later. For instance, the C standard was not related to the UNIX standard and was not originally championed by /usr/group - but rather the PC-based folks.
Remember, this document came about before the age of laptops. We made changes and suggestions during the meetings. The /usr/group document was edited offline after the meetings (Heinz may remember who did that work). We started the same process by the time we transitioned to IEEE. Since the meetings were originally held currently with a /usr/group // UNIForum or USENIX event, they were always near one of the Masscomp field offices. I told Jim that I could (and did) arrange for a loaner Masscomp system with a number of Wyse-60 terminals to be there for our meeting.
By the way, Jim was worried that all documents were following the IEEE rules of being numbered and correctly indexed. But by editing at the meeting and starting with the /usr/group document, we did turn it into an IEEE-style draft in under two years. As a result, I ended up as the defacto editor for the first few drafts. As I said, I believe I have an early copy (in troff, of course) on my Masscomp box.
Clem