At first I thought that my nsec was going to be attached to my account, I'm happy it's not. Thanks for making that choice.
I think it would be best if there was a spot to put in your existing nsec when you install the extension. Actually it should be have the option to create a new one or add your existing one. That would be the best flow.
It's strange that it just bypasses this step when you log in and I don't recall seeing any info about it during the install. It's caught a few people that I know by surprise. They thought their Alby account was broken with Nostr, but it's just the wrong nsec.