[Plugin: Multisite User Management] WP-FB AutoConnect multisite

Hi,first of all thanks for giving us this amazing must have plugin for anyone running a connect network.
However in one of my child site I was planning to use WP-FB AutoConnect.
https://www.justin-klein.com/projects/wp-fb-autoconnect
My mother WP is connected to bbpress and main purpose of the site is anyone registered in anywhere in network should get a forum account.
Problem is if I use above plugin in a child site my understanding was that your plugin would create a corresponding account in mother site which in turn would create a bbpress account.
However in the WP-FB connect plugin site I can see a premium option saying:
“The free plugin is not aware of users registered on other sites in your WPMU installation, which can result in problems i.e. if someone tries to register on more than one site. The Premium version will actively detect and handle existing users across all your sites.”.

I don’t mind paying for the premium version but my question is in my scenario is it necessary to archive what I’m looking for?As if FB plugin creates even one user in one site won’t ur plugin would take care of the rest?Or if someone signs up in main site as your plugin would create a corresponding user in all child site along with where FB plugin is installed so FB plugin should recognize user already exist and don’t allow duplicate sign up.Am I correct?
Would really appreciate your inside view on this.
Many thanks in advance.

https://www.ads-software.com/extend/plugins/multisite-user-management/