Yes, it does.

I have another AR750S with the same password, and it seems to work with the root password. The only difference is that the other one was purchased awhile ago (pre-3.009). I configured that one and then upgraded to 3.009. However, on this problem one it came with 3.009 already installed.

That sounds like a good point, perhaps I’ll try to flash an older firmware, confirm the password works for both admin and root and then re-upgrade.