Ok, so that may explain why mine seems to be able to be wired for >starting
through the key.
It's all how you connect the wires to the ignition switch.
If you choose to go the starter button way then you do not connect a wire to the (50) position of the ignition switch (the position that is spring loaded and acts like the car starter). Instead you run a wire from the fuse block (black and blue wire originally) through a starter button and then (brown wire) to the relay for the starter solenoid. Basically it is active all the time when the ignition is on. That is one thing I don't like about the starter button.
As for the car type method...you basically run a wire from the (50) position of the ignition switch directly to the starter relay.