New Roamio Plus woth MoCA and Old Premiere with 802.11n adapter stream fine ... Why?

This is just a question, not a complaint. My new Roamio Plus is set to use the MoCA network that is in my home thanks to my Verizon FiOS router (or is it the FiOS Optical Network Terminal that embeds MoCA?) My old TiVo Premiere networks via a TiVo 802.11n adapter hooked to its Ethernet port. I purchased a MoCA adapter for the Premiere under the assumption that I needed it to facilitate streaming between the Premiere and the Roamio Plus. However, I have not yet hooked the MoCA adapter to the Premiere. After I set up the Roamio Plus I tried streaming HD recordings in both directions between the Premiere and the Roamio Plus, and it worked fine. I did not expect that the two DVRs would even "see" each other, much less stream video from one to the other, given that they are set to use two different kinds of networking. Can anyone explain the fact that my Premiere does not seem to need a MoCA connection to stream to/from a Roamio Plus that networks via MoCA? Thanks.