The author deliberately used the term "LISP Machine", with all of the letters of Lisp capitalized, but that's an anachronism (and a fairly good shibboleth). When they were developed they ran Lisp Machine Lisp, not LISP. And as far as I know they never used the specific appellation "LISP Machines", where the word Lisp was written in all capitals but the word machines was not.

Edit: It's hard to distinguish someone's tone on the internet, but I did not intend to be captious or mean spirited. My point is that there are enough differences between LISP and Lisp Machine Lisp, a descendent of Maclisp, that the two are not interchangeable.