Lucky for some. I've always had interleaving in all properties in my area. One I was next door to the cabinet, this one about 200m from it. Always the same pings and interleaving depths. I was beggining to wonder if Zen had me on a stable profile.
Strange thing was the hg612 and the d6400 always report me as interleaved. The Asus always reported me as fastpath.
Interleave and Fastpath are not always reported correctly especially when G.INP is reported as being enabled. Technically G.INP is a form of interleaving, so when then the ASUS reports Fastpath it is not telling you the whole story about G.INP and interleave depth.
Most reliable test for me at least is to just ping google.com, anything 12ms or lower seems to be Fastpath and/or G.INP functioning correctly, if you getting 20ms or higher then either interleaved or G.INP possibly not working as intended and at this point need to check other factors such as what cabinet you on, line length, line noise etc etc.