How does that sentence support the idea that he knew "more about furniture than most"?

The bit you quote isn't even something he said! In the original post[1] it was assigned to "certain very old and very tired philosophers", but that's now been edited to just being credited as "a theory, not necessarily a really good theory".

[1] https://web.archive.org/web/20260523124615/https://www.mahl....