I’m not exactly sure I understand what you are saying but my best reading is - no, this is not a bug.
My reading of your words is that this is a bug because it happens automatically (untrue) and/or because it appears tied to a user’s profile (somewhat true but ultimately tied back to the Projects). I’ll explain below.
Prior to building Contexts, we developed a quick feature that allowed a user, if they have proper permissions on both projects,- to copy and paste environment variables from one project to another. I’ll highlight that is simply allows that copy/paste and it’s not a syncing process. It’s called “Import Project Variables.”
The API endpoints were a bit wonky but in the spirit of iterative development, we started with what we had. The import is only successful if you properly have the right permissions on both projects. It is tied to the User, yes, but only having the right permissions on both Projects. I believe this is what you are referring to?
Given the popularity of this feature, we developed Contexts and are likely going to depreciate the “Import Project Variables” in favor of Contexts in the future.