As far as I know, Orbi only supports VLAN bridging on the WAN side. Why should the router for fibre 7 have to be able to do that?
The following question also arises for me. If you order fibre 7, do you have a fibre connection and an OTO box or? As far as I know, the Orbi router does not have such a fibre connection. If you wanted to use the Orbi pair for that.
I also have fibre 7 and bought the router recommended by Init7. Since I had to hang it in the closet, I also bought this Orbi starter set. I use the Orbi router as an AccessPoint, which works wonderfully. For this, my Orbi router is connected to a Lan socket, which is connected in the wall cupboard from the OTO socket via the router.