Sort of... it's 1KHz PWM at 12V, modulated on the ground. But yeah still a simple circuit.
I used 12V LEDs which give some indication of "how locked" the diffs are (just by the brightness of each LED.) and have logged a lot of raw data while I was figuring out the system.
I've driving with the simple LEDs and data logging for a while; I don't think an accurate indication (like an array of specific LEDs.) has much value, as it's only an indication of the solenoid, not necessarily an accurate indication of the diff itself.
The LSD plates are "locked" by pressure from the gerotor pump. The solenoid is only there to release or hold that pressure.
So if you're driving straight in high-range with no wheel-spin, engage low-range, then immediately enter a cross-axle situation.
The solenoids will initially be engaged "100%" (and the LEDs will indicate "100%".) but the LSD will be essentially "0% locked", since there was no pressure built-up by any differential action prior to getting cross-axle'd.
That's just a basic example, in reality it's messier since there's always a bit of pressure pre-loading the plates and always some pressure bleeding off.
Also when in low-range, I've only seen the solenoids go "100%", I haven't seen them do anything other than engage fully.
They do activate gradually in high-range (which makes sense for helping with high-speed wheel spin or whatever.), and the pressure would be quite consistent in this case, but the logic is very conservative. As-in, they release pressure very quickly when differential is reduced.
So I think if you've got wheel-spin for more than a couple of seconds in high-range, you've probably got more important things to do than look at LEDs