I suppose only a specific PE knows the mac address for client A interface. Arp table in hub router never know mac addresses for CE devices.
By the way, I know one phycical interface can have many IPv4 addresses at same time. And one physical interface can also have both IPv4 address and IPv6 address at a time.
But, I suppose, one physical interface cannot have two or more mac addresses. Am I wrong? In other words, both IPv4 addresses and IPv6 addresses use same mac address.
Now we've got clarity of the problem. Which is the same two mac addresses in your arp table is normal and healthy. If your router can display arp table for IPv4 and arp table for IPv6 separately, you can find same mac address, which is mac address of the oppsite interface, is in the tables; which means arp processes work correctly.
The Scripture says, "Do all you can for everyone who deserves your help. Don't tell your neighbor to come back tomorrow if you can help today." [ CEV Proverbs 3:27-28]
My solution is that routers both in the middle and at both ends must have the data link layer which can get protocol numbers from data portion of L2 PDU so that it can pass L3 PDU for IPv4 to IPv4 protocol and L3 PDU for IPv6 to IPv6 protocol correctly.