Power measurement on neutral instead of line
Power is volts multiplied by amps so you need to simultaneously measure the voltage between live and neutral and the current flowing in live OR neutral.

Saying that power measurement is "neutral metering instead of line metering" misses the point about power measurement. You cannot measure power from one wire going to a load. 

You can measure current on one wire and it will be the same on either wire assuming no leakage to earth. But given that leakage from live wire to earth is probably bigger than neutral wire to earth, current measurements using the live wire will be preferred.