That is exactly what I did. And I got a temporary mailbox at the local UPS Store so they could not get my real address. And signup on their website was with a new email address. It’s a pain but it was worth it for me. Of course, I opted out of the DNA Relatives feature.
My sister didn't have an account when we sent the packages. When the data got analyzed it showed it as "My Sister" with close to 100% accuracy. The packages were anon, so they couldn't know which sent which.