I can verify this. Like other public beta testers on 12.1b5, I deleted the beta profile, went to Settings > Software update and was shown iOS 12 not 12.1.
I installed anyway and got iOS 12.1, build number 16B92 which is the correct build number for today's public release of 12.1.
excellent....with Apple no longer signing iOS 12 any more (unless the guy running the OS headers runs the signing servers :0) it was a measured risk...