Do you have a source for claims that (a) google parses emails for purchase histories and (b) sells it?
https://myaccount.google.com/purchases is empty for me, and I sure do have a lot of email receipts on my gmail.
It also says "Purchases made using Search, Maps, and the Assistant are organized to help you get things done, like tracking a package or reordering food".
https://mail.google.com/