Ralph,
Sorry you're having the issue. I'm a little confused as to what's causing the problem, and your solution though. Are you saying that you simply change the setting in the JFBCLogin module to use Joomla instead of JomSocial, and that fixes things? All that setting does is change where the Register for this Site and Forgot Password links go to. It doesn't affect the actual Facebook registration process at all.
We definitely test with JomSocial 2.2.3 and haven't heard of this issue before, so it's hard for us to make much progress without seeing it in action. If you want to PM me any more details about your site, or an admin account to see your configuration, we'd gladly look into it further. If you're interested in the types of automated testing we do (just to give you a little more confidence that I'm not just blowing smoke about our testing), check out this quick video which shows a portion of the testing we perform before each release, and when updated versions of the extensions we integrate with are released:
www.youtube.com/sourcecoast#p/a/u/2/zNGdc4_bv5w
Thanks again for your feedback. We will be testing more, but if you can help clarify the exact setting that fixes the issue for you, that'd help a lot!
Alex