Does the starter relay 12v battery post need 12v?

The ST wire closes the relay off the ignition switch when in key start.
But you would still need 12 V like a typical relay once the ST wire is energizes to close the circuit.
The wire to solenoid and wire on relay aren’t connected until ignition energizes and closes the circuit.

But hey. If there is a mass of goofiness just pull it and see if it starts?

I like the idea of getting all that extra junk off the terminal though and running it though am independent bus bar.