FWIW, I'm on Mac OS X running this with emacs -Q:
GNU Emacs 25.1.1 (x86_64-apple-darwin15.6.0, NS appkit-1404.47 Version 10.11.6 (Build 15G1108)) of 2016-11-11
If I click the little "maximize" button I get a frame with the (fullscreen . fullboth) parameter. According to ancient tradition, let us all praise Emacs' distinctive naming conventions.
From a maximized frame, I cannot get (make-frame) to create a non-maximized frame. I've tried setting the fullscreen, height, and width options of default-frame-alist, and I've tried passing various combinations of the same into the make-frame function. No joy.
What am I missing?