3a spells out what you're agreeing to share with the publisher of the product in the marketplace when you subscribe to it.
Additionally the listings each link to their respective privacy policy right underneath the subscribe button, plainly in view above the fold.
Finally, I've just attempted to subscribe to "Ubuntu Server" in the Azure Marketplace to see what it looks like, and it shows you a form with the information it's going to share with Ubuntu on the screen for you to modify before subscribing! So it seems like you arguing this isn't "obvious" is in bad faith, because it's obvious for any reasonable person who's actually used the marketplace.
