That configuration is set to allow the Nextbox Whole Home PVR system to use the D-Low band which runs from 1125 to 1225 MHz edge to edge (100 MHz wide).
As a result, if you choose to use the modem as one half of the adapter set, thereby only buying one adapter, you are accepting the restriction to use the D-High band, as determined by the modem's D-High band configuration. That loss of 100 mhz in the D-Low band will restrict the data rate as shown by @darryldale running 800 Mb/s thru his Actiontec adapter. The datasheet for the Actiontec ECB6200 indicates data rates over 1 Gb/s, but, it doesn't provide an exact theoretical number.
If you don't have the Nextbox Whole Home PVR system running, you can still use the modem as one of the adapters, but, you would still end up the modem using only the D-High band for MoCA operations.
If you don't have the Nextbox Whole Home PVR system running, that allows you to use any other MoCa adapter set as an end to end set or system. In this case, the adapters should allow you to use the entire D-Band, running from 1125 to 1675 MHz edge to edge. That would allow you to use the max data rates provided by the MoCA adapter set.
There is also the goCoax adapters are also in the same category, 1 Gb/s end to end, once again most likely due to the use of 1 Gb/s ports, but also claims to run 2.5 Gb/s throughout the network: https://www.gocoax.com/
Once final note, if you're running the Nextbox Whole Home PVR system, which uses a MoCa network to transmit data between the Nextboxes, or any other MoCA network, you're going to run into a potential problem with the adapter selected MoCA network controller. You're better off with the Actiontec Adapters as they allow the selection of the D-High band and a user selectable Lowest Useable Frequency, which can be used to set the adapter frequencies above any existing MoCA network, thereby separating the two MoCa networks. That forces or allows the Actiontec adapter to ignore the existing MoCa network controller in the lower D-Band and use its own chosen controller for D-High operations.
The goCoax adapter also allows the user to set the lowest usable frequency, but, these adapter don't appear to ignore the existing Network controller in the system and as a result, you run into problems as the goCoax adapters want to be the only active MoCA controller in the MoCA network system, even if the adapters are set to use the D-high band only, supposedly ignoring the D-Low band. The Nextboxes don't like this at all. End result, you appear to have to make a choice, Nextbox Whole Home PVR system, or, MoCA network using goCoax adapters. There is nothing in the MoCA spec which indicates a hierarchy for the MoCA Network Controller, ranging from the MoCA 2.5 spec controller and downwards from there to MoCA 1.1 controllers which are probably what the Nextbox has onboard. My guess would be a bug in the firmware or a deliberate choice for some unknown reason.
Just to mention this at the present time, Rogers is theoretically getting ready to run a DOCSIS frequency extension up to 1218 Mhz, which overlaps with the lower MoCA frequency of 1125 Mhz. Techs are now installing updated Antronix splitters and amps which run up to 1218 Mhz. The actual flip of the switch could be several months if not years away, don't know, but, keep the possibility in the back of your mind if you're running a MoCA network using the whole D-High Band. If and when that happens, MoCA users will have to be ready to reconfigure their adapters to run in the D-High band only.
Docsis 4, if it ever happens appears to run up to 3 Ghz, taking up the entire cable bandwidth. If that ever happens, the MoCA Alliance will have to decide what to do about it. From what I remember, Comcast has pulled out of the MoCA Alliance, so, there might not be any more MoCA frequency changes down the road. Perhaps this is the end of the road for MoCA development? Don't know. For that matter, DOCSIS 4 is also a question as Intel has sold the Connected Home division to Maxlinear, who manufactures the cable tuner for Intel's modems, and, Broadcom is looking for support (ready money) from ISPs for develpment of DOSCIS 4. The ISPs appear to be rather reluctant to hand Broadcom a fistful of dollars for some reason. So, between the two of them, as the industry leaders in DOCSIS hardware develpment and deployment, I'd say that there's a chance that DOCSIS 4 doesn't happen. The spec is out, but, perhaps, after transitioning to DOCSIS 3.1 upstream (which Rogers has yet to do), there might not be any further push for cable data rates beyond DOCSIS 3.1. All speculation on my part, but, there a considerable amount of money involved, which companies don't appear to be willing to spend.
Thank you for the useful information. I'm a cable-cutter so no PVRs in my home. My primary motivation for MOCA is getting faster internet speeds vs wifi mesh through the house. I have not been able to find a Canadian retailer that sells GoCoax Moca 2.5 and Actiontec ECB6250 so I would get the Actiontec ECB6200 since GoCoax is out of stock.