I don’t know why the plugin was listed when you searched for OpenID plugins. As Ciudy said, the plugin description clearly specify the list of supported providers.
I’m not the original author of this plugin so I don’t know why it was created supporting only Yahoo and Google instead of supporting any OpenID provider. Actually I have asked myself the same question when I started maintaining it.
It is on my list to change this and support any OpenID provider but I’m not sure when I will have time to implement it. If you are a developer and you would like to contribute, patches are welcome. See https://github.com/thenbrent/social-connect/issues/44