Today I used the browser extension to generate a password and also got a one-time password at about the same time. These were for the same account, but I temporarily had them as two separate logins in 1Password.
Later, I copied the password from the first login to the login that had the one-time password. I saved. I clicked back and forth between the two a few times to make sure I didn't miss anything.
I noticed that in the login where the password was first, the strength bar is filled all the way to the right. For the second login, where I just pasted the password in, the strength bar only goes about 90% of the way over.
1Password Version: 6.8.1
Extension Version: 188.8.131.52
OS Version: 10.12.6
Sync Type: Dropbox