George's comment is correct. If the amp were cathode bias, no adjustment would be needed.
If the idle current is higher it will stress the tubes.
You are better off with too little than too much!
Adjusting the bias current and the voltage are really the same thing- the voltage sets the current through the tube(s). What you are measuring is either the current itself or the voltage that it induces across a resistor, but either way you are measuring the same thing- the correct current through the tube.
Are the tubes stressed by being off the bias target setting? What would be good plus-or-minus numbers be for each? Why did one designer choose manually setting bias voltage and why the other chose manually setting bias current?
If the idle current is higher it will stress the tubes.
You are better off with too little than too much!
Adjusting the bias current and the voltage are really the same thing- the voltage sets the current through the tube(s). What you are measuring is either the current itself or the voltage that it induces across a resistor, but either way you are measuring the same thing- the correct current through the tube.