There is no such thing as 5ms VOIP audio latency at 6 Kbps, the IPv4+UDP headers would amount to 44.8 Kbps at minimum, so it's irrelevant if one encoder is tuned to be able to encode 5 ms chunks instead of 40 ms chunks. 40 ms intervals requires a minimum of 5.6 Kbps + the codec rate.
I.e. at 10 Kbps it's impossible to have a lower VOIP latency than 32 ms. Likely the 40 ms number they tuned for in the real world.
I.e. at 10 Kbps it's impossible to have a lower VOIP latency than 32 ms. Likely the 40 ms number they tuned for in the real world.