It is definitely well-supported -- I recommend reading http://www.catb.org/esr/writings/taoup/html/index.html (available in print too)
Re:Doug McIlroy on Unix Taste (2014)
by GFK_of_xmaspast on Friday June 10, 2016 @03:48PM
(#11879446)
I don't consider ESR to be an expert in anything except promoting himself.
I'm not sure how well-supported this is in the historical record.
You give /proc as an example, but it's first appearance was in the 80s, and it took until solaris in the early/mid 90s to really get going. ( https://blogs.oracle.com/eschrock/entry/the_power_of_proc )