For FYI, OP:
I believe that in a standard installation, use of the Ethernet at the Joey is used ONLY for access to the internet for Dish apps and downloads or streams of content, and does NOT take the place of the MoCA delivering TV or DVR from the Hopper units--but MoCA is not used for apps and download or stream of content: that would be the result of turning Bridging OFF.
In the Network Settings, it gives status of either the RJ45 being active or the MoCA being inactive or active--but only as it relates to INTERNET access ONLY. And in my situation (MoCA 1.1), I always have bridging OFF so that the MoCA is kept as clear as possible so that the speed of multiple downloads of content are not compromised by the number of users on all the Joeys--of course, this means I have wired Ethernet in all the rooms. If one does not have access to wired connection for the Joey, then Bridging becomes necessary.
Now using the RJ45 port on a Joey to REPLACE the MoCA for sending live TV or DVR events from the Hopper to the Joey is a completely different matter, and as stated by others, can be accomplished and is being used as such by some members here (nice thing to know), but is not officially supported by Dish, so people use it as long as it works. Also, as stated by others, this can be taxing on older routers causing excessive heat or other hiccups (due to limited memory too many streams or devices, etc). I know of no way for the Joey to access, using the RJ45, any devices other than the Hopper or your gateway for internet access. Others may know, but I don't.