I have used the same type of component tester. Test of 2SD1071 ST901T BU931T all darlington type ignition transistors that work in the circuit.
Your measures shown makes it even more evident, that the HFe are not that major, but that the Uf seems highly important. Can someone explain that for a 'dummy' how that would be possible...KISS?
I'm lost when paddling through the datasheets
The one with 17 in hfe and 1,01 in uf are one from me, else being Debe. Basically it’s watch the tester are doing, and some add a test frequence, sinus curve.It's odd that 689 mV would be a darlington.
I think Uf gives an idea of junction quality, but with darligtons you have 2 in series. What if one is 0.3 and the other 0.3? Then you can't tell of 0.6 is good or not.
But Hfe is very dependent on Ic based on the graphs. Thus putting a circuit together with 2 resistors to test at a higher Ic might be beneficial. Just divide Ic/Ib for Hfe.