High Bill,
I’m no expert either but I think the old style meters you mention did indeed have two coils in them set at 90 degrees apart, one being primarily set up to give a field depending on current and the other on voltage which then gave you a quite clever way of discerning the phase angle between them by the direction and speed of the rotating disc. If you are in perfect phase (phase angle = 0) as in your suggestion the old meter would stop turning. In practice it is quite tricky trying to maintain unity power factor in a house as you’d have to continually adjust the capacitor bank in relation to the inductance of whatever you switch on or off but would result in a low electricity bill :). This isn’t (I don’t think) the same thing as watt less current where you try and aim for 90 degrees and thus purely inductive. As the watts = VI cos phi and cos of 90 = 0 then watts is zero independent of what V and I are. << going off on a tangent.
Ahh those old typos they always get me.... 