What is actually the point of LiHV? To be honest I don't see any. You want more power? A 3S LiFe has plenty and is more safe. I don't see any benefit in a LiHV.

And regarding the ETS picture - thats the overall voltage of the battery and charging leads. With the high charging currents it will always be slightly higher due to resistance. On my charger the voltage on the balance connector (where there is no current) stays at 4.20 max, while the overall can get up to 8.43