I’m sorry this happened to you. I am reading your post a year later because a similar problem just happened to me. I am not ready to go into details yet because the issue is not resolved, and I have yet to hear back from Proton. The fact that this is happening during the holidays when responses are slow makes it even more frustrating.
What I can share is this, Proton synced my Proton Pass and SL Logins aliases without my consent. I did not ask them to do this. A Proton Support agent just did it in an attempt to fix/investigate a problem I reported. They didn’t tell me what they were doing, and it didn’t fix the problem. I am very upset.
It is also my understanding that the sync cannot be undone, but I came here to ask if you are 100% sure because in my case I did not do the sync or ask Proton to do it. They did it without my consent, and without warning me first. I’m so angry. 