You're right, G.hn will have the same issue as DSL here; all of the tiny bridge taps from the extra jacks will create small dips in the bitloading.
That being said, with 200MHz of spectrum to play with, the impact on rates should be negligible. With the 200MHz G.hn phone line profile (48KHz tone spacing), we get about ~1.5Gbps, so you can take some lumps and still get ~1Gbps throughput.
One big advantage though, G.hn is natively p2mp and each jack could have it's own G.hn endpoint.
