mozilla-services/android-sync — comment on commit c0c8705c38f29bef2df7ae9c0c3184314be2ff6f
File: src/main/java/org/mozilla/gecko/sync/repositories/android/AndroidBrowserClientsDataExtender.java line 28
By rnewman:

I think I see what you're saying.

IMO, the account GUID is the GUID of the record on the server. That will be globally unique. The profile column just indicates which profile this is for (which might be redundant, but is harmless). We know which Sync account we're connected to implicitly.