A true pyramid bow has an even thickness and the tiller comes from the side taper. Any bow that has a straight taper from the handle to the tips is considered a pyramid style bow, add a few inches out from the handle before tapering is called a semi-pyramid.
I've made many pyramid style bows but never just tapered from the sides. I cut the limbs to pyramid shape and tiller from the belly...and some side tillering if the limbs are getting too thin.