The 2.5 Gig port of Orbi is limiting network speeds received by the ISP Modem

I ordered the Netgear MS305 2.5g switch (which is currently on sale) to replace my TRENDNet TEG-S350 2.5g switch in my garage as it has a known issue causing ghost satellites to show up in the orbi app (no other noticeable issues, but figured this problem was annoying enough to solve because it also causes the firmware update in the app to error out).  The new switch resolved the issue with the ghost satellites and so far is performing very well.  

I also tested putting the TRENDNet 2.5g switch in front of the RBR850 connected to the 2.5mGig port of the XB8.  This is where things get interesting.  The WiFi speed I got directly from the RBR850 was insanely fast (840Mbps).  Additionally, the LAN speeds from my ethernet backhaul SAT were only reduced to 700-750Mbps (instead of 450Mbps w/out the switch between the XB8 over the 2.5g port).  LAN Internet speeds directly to the RBR were around 800Mbps, BUT  speeds using a 1G usb-c adapter directly on the 2.5g switch was also reduced to around 800Mbps (getting the full 940Mbps when connected directly to any XB8 1GbE port).  Connecting a 2.5g usb-c adapter to the switch of course provided full internet speed (1150Mbps).  My conclusion is that although the 2.5g switch helps the Orbi, it actually has similar issues with the XB8 when connecting 1GbE devices to it (slightly reduced speeds vs using a 1GbE port on the XB8).  This leads me to believe the issue is with the Xfinity XB8 modem and not the Orbi.