Orbi Pro AX6000 Speed Test Should be Double

"Just under 100Mbps" is a highly suspicious number.  It often indicates that the Orbi router and the ISP device have negotiated that the highest speed they both support is Fast Ethernet, i.e. 100Mbps.  This process, called Auto Negotiation, is built into the Ethernet hardware on each device.

https://en.wikipedia.org/wiki/Autonegotiation 

Very often, it indicates a problem with the physical link between devices:

• The actual cable may not support speed greater than 100Mbps
• The cable may be defective.  100Mbps requires only two pairs of cable.  Gigabit Ethernet requires all four pairs to be present and terminated correctly.  If even one wire is not crimped correctly, both ends will determine that 1000Mbps is not possible and the connection will settle on 100Mbps.
• There may be something wrong with the RJ45 jack on one end or the other.  Perhaps one of those tiny gold wires is bent or not making good contact.

Swapping the cable is an easy test. (as well as taking a close look at the RJ45 jacks.

This condition can be confirmed by looking at the Orbi router description of the WAN port connection.  If it says "100Mbit/Full" instead of "1000Mbit/Full" then this is the case.

On the residential Orbi product, the web interface Advanced Tab home screen has a blue box "Show Stastics".  This is described on page 171 of the SXR80 User Manual:

https://www.downloads.netgear.com/files/GDC/SXK80/Orbi_Pro_WiFi_6_UM_EN.pdf 

p.s. getting the ISP to confirm that the correct speed is being delivered is absolutely a good step.  What some users do is temporarily connect a laptop directly to the ISP device and test the speed.  With more and more computers and laptops now lacking Ethernet ports, this is becoming harder for many people to do themselves.