Warm air rises. Cold air falls. I think everybody will agree with that.
tMax therefore makes sense as a sampling at 2 meters in a shaded place that will closely measure the likely maximum air temperature for the day.
But tMin? Should that also be sampled at 2 meters?
Well the temperature profile is considerable different at night to the day. Cold air falls.
Would it not, therefore, if we are trying to re-purpose the ground instruments into a volume air temperature measuring device, be reasonable to place the tMin sensor closer to the ground? To accurately measure the air volumes above.
Then it should be able to accurately determine the energy/temperature in the whole air column, rather than just the more limited volume above 2 meters that it does at present.