Large milk dough for pizza; doesn't seem to knead at all
Probably a combination of causes. You're using whole wheat flour, which really does not knead like white flour, even used in moderation with other flour: in addition to having less gluten, the shards of bran cut through the dough structure as you knead. Particularly if the &quot;refined flour&quot; (hmm) you were using wasn't high-gluten bread flour, that could leave you with very little cohesion. The olive oil will also interfere with gluten formation, as will the milk to some degree, particularly whole milk.
Now, none of that may actually matter. Pizza doesn't need a gluten matrix for structure in the same way a free-form bread loaf does, and the recipe you've chosen indicates that you're not looking for the classic Neapolitan crust texture anyway. If you're forming the pizza on a pan, you don't need the gluten to pull the crust, and the starch gel that forms during baking will make it hold together just fine as a cooked pizza. Treat it like pie crust, and roll it out instead of pulling it out.
Oh, incidentally, 10 tsp is a real weird measurement. It's just shy of 1/4 cup; use that instead, and give your measuring hand a rest.