No, test the power wire only disconnected from the coil. See if it reads near battery voltage like that and then is drawn down to 10 volts once you connect it. Honestly, I don't think I ever tested the coil power feed wire connected to the coil. I think I always had it unplugged when testing it for battery voltage. Maybe it's normal for it to be drawn down a volt or two once connected? The reason I've tested some in the past is because low voltage to the coil is a pretty common problem on old bikes because of all the old connections and switches the voltage must pass through to get from the battery to the coil. You can lose several volts if those things are all crusty and dirty. But you say all your wiring and switches are new, so you shouldn't be losing voltage, at least not several volts. Maybe you'd see a few tenths of a volt drop. That's usually what I end up with after cleaning everything.
If you are getting 10 volts on the power wire with it disconnected from the coil then you need to start tracing it back and checking at every connection and switch to see where you're losing that 2.7 volts.
If you are getting 10 volts on the power wire with it disconnected from the coil then you need to start tracing it back and checking at every connection and switch to see where you're losing that 2.7 volts.