Sure. But either way, the issue remains. Just removing or hiding the form content doesn't stop someone submitting to that form.
The whole idea of Shopify is to make workflows flexible and logical out-of-the-box, and the way this function has been set up, there are limitations that could easily be removed if it was done properly. I see the 'Accounts are required' option as not yet truly functional.
EDIT:
Or just restrict content until the admin gives them a tag or certain metafield.
That's an interesting idea. Wouldn't the client still be logged in automatically though? Or are you suggesting that doesn't matter, and that you could wrap hidden elements using a tag in their account?