Sure they could... What do you think there were doing when they were selling System III & System V?

They compiled customer lists, and sales contacts, contract agreements and everything else you'd expect from an org selling commercial software. Was it "automated" in the same way that tracking use from a package manager is? No. Was it tracking? Fuck yes.

Unix wasn't free until the FSF began the GNU project...

Hell, even the BSD variants of unix were sold - they weren't free software. Are there free implementations that exist today? Yes. They exist because the item being sold and maintained by the corporation is NOT the spec for the language/os (the recipe) it's their implementation of it.