Best way to move from php-mysql to php-mysqlnd

I gave this a try and ran into the error of old_password. Looking in the main mysql database in the shell, I see all my users with the old 16 char hash.
So I deleted old_password from my.cnf file and when I edit a user or create a new database user it has the new 41 length hash.

So my plan was to just go into each account and edit the password, just setting it to the current password (by looking in the database connection file for each site wordpress or custom). Then once that's done I can enable the new mysql plugin without issue.

BUT... I ran into an issue with phpMyAdmin and the main SiteWorx user (automatically created by InterWorx).
Example
SW account abcwidgetstore.com with account username of abcwidge with a created DB username of Bob.

In the mysql user database it would have:
abcwidge
abcwidge_bob

With old_passwords set to 0 or commented out when trying to access a SiteWorx account the main user (abcwidge in this example) that is created on the fly is created with a 41 char hash. Which is a good thing I thought, but then you get connection errors when trying to open phpMyAdmin.

What I don't get is why is there an error there at all? I set a few accounts (manually created DB users) to the new 41 hash and am still able to connect to their databases via PHP scripts, so why won't phpMyAdmin?