I think you are confusing several different kinds of accounts, all of which are for different purposes:
• Your Affinity forum account, necessary if you want to post anything here. Obviously, you already have that.
• Your Apple user account, necessary for purchases from the Mac App Store, the iTunes Store, & to use various Apple-provided services. This account is tied to your Apple ID. Serif/Affinity has no access to your Apple ID or anything tied to it, including your Affinity purchases made through the Mac App Store.
• An Affinity Store account, necessary if you want to buy anything that store sells, like the Workbooks or the Windows versions. This included the 'bonus' content offered for free -- even though the price was zero, it was still considered a purchase, in much the same way as many free apps purchased through the Mac App Store are considered purchases.
• A Microsoft user account, necessary if you wanted to buy Windows apps directly from Microsoft. Much like the Apple user account, Serif/Affinity has no access to that.
You can use the same email address for all of them if you want, but you still have to set up each of them separately, supplying whatever personal or billing or other info they require to establish & use that type of account, including whatever email address you want associated with that specific account.
