In order to say it with certainty I need to look at the wiring diagram. I have factory repair manual for my MX-4700. If I get a chance I will look at it on Monday. I actually bought a
L4600 DT but realized later it was not built in Japan. I then changed my order to Mx-4700. They have a lot of similarities . The key switch is always powered on but it routes power to gauges when you turn the switch on . In your vehicle when you turn the key on , instrument light will come on along with gauges and then next turn closes the start up relay to switch power to starter circuit. It is like that on my Ford 1700 also. I have not gone deep with my Kubota as I had no need to do it yet. Do you have a multi meter? that might come handy for diagnostics. Do you have WSM (WorkShop manual)for your Kubota?