RBR750 not able to connect new RBS750

I have a RBR750 router wired directly between a Spectrum modem and a LUXUL switch that feeds to ethernet ports around the house. The home has spray foam insulation in all walls (even internal) and solid wood doors which makes wifi propegate really poorly. I have two RBS750 wired to ethernet working as satellites for the system. I still had deadspots in one end of the house so I bought another pair of RBS750 satellites. I cannot for the life of me get these two to work as expected. They appear as attached devices (ethernet is working), they are on the same firmware (V4.6.5.14), they even seem to be acting as a wifi extender (I can see connected devices in the satelitte detail page) they just dont show up as 'satelittes', rather as network extenders.

I am interested in 2 things, thanks in advance for anyone who has ideas/thoughts!

1) Does a RBS750 connect via ethernet, which shows up as a 'generic' netgear wifi extender, have any functional limitations (besides not showing in the newtork topology, and not appearing as a part of the 'updateable' hardware)? AFAICT it is working as a network extension. 

2) Does the RBR750 support more than 2 hardwired satelittes? I have them configured using the setup including an ethernet switch as depicted here https://kb.netgear.com/000051205/What-is-Ethernet-backhaul-and-how-do-I-set-it-up-on-my-Orbi-WiFi-System

Thanks for any suggestions, I have included some images of various configurations/pages for context.