An explanation, maybe....
Due to the hysteresis span of the thermostatic switch plus the level of liquid refrigerant remaining(system cooling "coast" time) in the R/D at clutch off time the low IR you got might be perfectly normal.
The time constant of the compressor on/off periods is fairly long, you might well measure a sub-freezing temperature, especially during the initial clutch off time ("coast" time) as long as the switch hysteresis causes the clutch circuit to remain off/open for and equal or slightly greater time with the evaporator above the freezing level.
Result, the AVERAGE evaporator core temperature over the complete system cycle time is slightly ABOVE freezing.
Hold the
PR trigger on for an entire system cycle period, or even several, and then check the min/max readouts...
