Lovely job, I like the "here's where I've got to so far" style. This gives people enough to work from and make a hand-wired version while he's waiting for boards to come back. Even if he runs out of time to do anything it's leaving a working design and firmware for folk to start from.
It's definitely too easy to put off publishing until it's "properly" done and then it never happens.
I think he might have been calling into question the wisdom of using the standard telephone network to directly place voice calls. Technically it's encrypted but your privacy is anything but guaranteed.
This project uses the same AG1171 SLIC module; it's just not enough by itself and still requires a microcontroller (or at least non trivial logic) even before you get to processing the audio streams.
It's definitely too easy to put off publishing until it's "properly" done and then it never happens.
https://youtu.be/nibV_idJjlg
https://www.ebay.com.au/itm/305557776577