You’d be surprised by how many shops don’t have a lathe with enough swing to face a flywheel. And yes, they should be ground. And they are ground with the crank flange sitting on a parallel ground spacer or something so the face is parallel to the crank flange.
I suppose you could make a fixture to bolt to the FW so you can Chuck it in a lathe and face it, but that’s way more work than it’s worth. FW grinding is relatively inexpensive.
