Avoiding the term "Ethernet" altogether, because cat5/wireless/moca can all be ethernet at some level.
The only thing that traverses over the cat5/wireless connection by default is communication to/from the internet - internet sourced VOD data, "call home" data communications with dish, app data like Facebook/Pandora/Weather Channel app/music channel album art/etc - and the "second screen" apps like DishAnywhere and Dish Explorer. All in all it's really a trivial amount of data.
All video from Hopper to Joey/SJ to Hopper/Hopper to Hopper will traverse the coax/moca connection if available, Dish doesn't want the core video functions to be dependent on non-Dish hardware like a router of unknown quality.
The satellites provide all data needed for core functionality - live programming/guide data/channel logos/tile images/etc. Data coming from the satellites travels the coax, but at different frequencies than moca and does not impact moca bandwidth.
For an internet connected system, the phone line is used for caller-id and not much else. If not internet connected, then the nightly "call home" from the STB to Dish goes over the phone line.
The net result is all the extra connectivity doesn't really gain you any extra capability - by default.
As we know, Dish did not hard code a moca only restriction into Hopper/Joey. If moca is not available, the components will find each other and communicate over the cat5/wireless connections. It would therefor be possible to gain bandwidth by not connecting a device via coax and forcing the data to ride over cat5/wireless. The best example is the user who disconnected the SJ integrator from the node and forced all SJ communication to go over cat5, in effect eliminating all the extra bandwidth required by the SJ from the moca link.
But cat5/wireless is not supported for video, there is at least one feature that does not work correctly over cat5/wireless, and there could be more. The one I know of is the DVR drop down on a cat5 Joey only sees the linked Hopper in a dual Hopper system. It's a nuisance issue, since the Joey can still link to either Hopper, but it shows not all the "plumbing" may be aware of the dual connectivity capability.