So I tested it and got the following:
The G36 engine shuts off once there is <= 3 gallons of fuel in the active tank (roughly 8% of the capacity!).
At this time, the corresponding gauge is just in the yellow (left tank was active):
Even if I set both tanks to 0, no warning shows up.
In the G1000 on the C172 there is such a warning for each tank separately shown in the PFD (both tanks set to 5% quantity each):
So there clearly is something missing on the G36 to warn you which is even more critical since one has to switch manually (opposed to the C172, iirc).
Oh and also note how the OIL PRESS is flashing on the MFD but the G36 is missing that warning on the PFD as well… I’m not sure if those warning were disabled on purpose since basically the G1000 interface is the same for all of these aircraft.