No, it's towers are "swirling with all the Winds of Magic". Nothing about one Wind to a tower, or any indicator that the Winds are actively being used for anything. The Colleges could easily build a set of towers that each attarct one Wind, so even if it is one Wind to a tower, no indicator that he could use more than one.
A Tome that may or may not exist in quest and is mostly about his desire to build flying buildings with no mention of any other details is useless in determining anything about him other than that he existed and wanted to build flying buildings (literally all that is said of it is "Fozzrik wrote of his desire to create buildings that would move from place to place, cutting out the need for roads; where trade between towns would flourish when they contacted each other - in a quite literal sense - and whole cities coudl take to the air to traverse dense and dangerous forests or avoid rampaging armies"). And also, Fozzrick canonically disappeared with the Fastness. Presumably after writing his book, he got it to fly and then never came out again, so the book likely doesn't attribute anything to him.
Honestly, nothing about the description of the Fastness actually requires High Magic at all. A very good knowledge of how to attract Winds, sure, and an incredible enchantment to get the thing to actually fly (canon says Fozzrick used a spell to make the stone it's built of lighter than air) but nothing I would see as impossible using one Wind, or a Windherder skill like Mathilde's. And of course, even if Fozzrick did use more than one, why is there any assumption he wasn't generating Dhar when he did so? Frederick Van Hel proves one doesn't go evil overlord immediately, and Fozzrick was already more than a little mad to start.