We're working on improving these emails. The first stage was adding an explainer section at the top of the email that answers the most common questions we've been getting surrounding purchases.
The next stage will be to show appropriate information, based on the order type (free upgrade vs paid order).
These order confirmation emails are the most concrete way to assure you're getting your free update. We're going to keep our free update promise, even if we nag you a bit to remind you that we're updating you for free. If we don't nag you, then most customers ask where their update is. The more information we can provide, the easier it is for us to support questions you might have.