I am not sure of a concept of MPLS regarding the difference between BGP IPv4 and BGP VPNv4. I am going to tell it below. If I am wrong, please correct me. Thank you.
I think the BGP IPv4 here means a regular BGP IPv4 address system, like IGP ip address system, while BGP VPNv4 is a special address family, which is BGP IPv4 address plus RD(router extinguisher) and is able to handle unique address between PE routers.