- The report suggests that ECI modems can support G.INP downstream, but not upstream. This ought to imply that most cases of extra latency should only be 8ms, coming from fallback of just the upstream.
I did notice the Billion 8800NL has phyr turned off on the US by default could that also be related to the above 
it appears the majority of modems have it turned off on US by default, presumably because its optional and therefore not all DSLAMs will support it.
From some tests last week, didn't we see that the modems (visibly) have the
PhyR feature turned off upstream, but that this is a different feature from
G.INP. PhyR is a Broadcom-proprietary solution, while G.INP is a generic ITU specification.
The modems make this hard to determine, because they seem to have separate command options to set the 2 features, but don't have options in the display commands to show both configurations in parallel.