I was hoping to add my Matter Bridge(s) to both both C8 and C8 Pro hubs...
Unfortunately, it seems that this is not possible as Hubitat C8 and C8 Pro detect the Matter Bridge with the same fabric ID when trying to pair it
And, in order to add the Matter Bridge to C8, for example, then I need to remove it from C8 Pro first, this is quite dissapointing as C8 and C8 Pro are two different hubs?
Did migrate from the one hub to the other without a reset? That's one possibility for how this could happen; the other is a failed pairing, which I don't see evidence of in your screenshot (assuming the one there is the other hub) but I suppose could still happen and just not have made it far enough to show on your other controller.
Each hub has its own Fabric ID (or should), which you can check in Matter Details.
If using Matter (and you wish to erase Matter configuration), navigate to Settings > Matter Details, change the URL ending with /hub/matterDetails to /hub/matterDetails?fullui=true, and select Reset Matter there.