Paying for Scientist will not put your email on the server.
Subscriptions go through the App Store in the Mac and iOS apps and through Stripe Checkout on the web. The server learns an entitlement date per account, and for web purchases a Stripe customer id. It does not learn who you are.
A paid service has to charge, send receipts and say when a card fails, and the obvious identity for all three is an email address. An email held by the server is the one fact that turns "an account" into a person, so it was the option rejected. Apple holds the identity and the money for the apps; the server verifies a signed transaction and stores that the account is entitled until a date. On the web, the server mints a Checkout link for an account id and Stripe holds the email and the card. Receipts and failure notices come from the payment provider, never from Scientist. One account carries one entitlement whichever way it was bought.
This is a change to what the server can see, and the security page says such changes are recorded here with their date. The row it adds is small but real: an entitlement date, and for web purchases a customer id that, together with Stripe's records, is a link someone could compel. It goes into the table on the security page in the same change as the code that stores it, and no such code exists yet.