parentheses in Lisp: Fake-news?

Today was a a discussion about a not-too-relevant footnote about the origin of Lisp-parentheses.

I did not surf too much, but here's some finds: the quotes of some

original paper in the following link

http://www.gigamonkeys.com/book/syntax-and-semantics.html'

seems to confirm what I said (namely that it was planned to add M-expression to the lisp S-expressions) but it never came around (or never gained acceptance).

The following one discusses that List-expressions are just a representation of ASTs

http://mnielsen.github.io/notes/parentheses/index.html

Martin