Yeah I understand all that, but I asked what they expect to gain by further improving the leads, i.e. beyond the already-superb Probe Master 8100 they already have?
I don't see an 8100 model, so I wanted to be clear that the pogo pin style was what he has. If not, there is clear improvement to be had by going pogo.
As for further improvement, as I mentioned sometimes Kelvin sensing is impractical and the Fluke 2X4W system gives you the convenience of normal probes with much better performance, perhaps 100X better than a typical 2W setup. You can also get a probe set from Pomona the does something similar with almost any 4W-ohms meter. I tried making my own, but was unable to source a decent tip end and the ProbeMaster SS tips don't work well enough. If the OP has a compelling need to do low-resistance measurements with probes, than this is the way to go.
Your 2-wire 4-wire test is interesting. Are your 2-leads compensated for in any way? I ask because if they are not then we know something is perhaps off with your tests? Each test wire is expected to have more than 1.46mOhm per foot.
I did a little data searching, apply some physics. The best economical wire is likely gonna be silver plated copper wire. In kinda ideal circumstances such wire that is 12awg will give us approx 1.46mOhm per 30.48cm (1 foot). That's just for wire. Need to also account for junction points of different metals.
If your test leads are 1ft each and 12awg, we should expect to see your meter pick up a diff of ~3mOhm between 2-wire and the 4-wire test.
Your meter seems to only show a diff less than 1mOhm, displays closest 1mOhm (assumed to be from rounding), etc. Each probe wire is expected to be more than 0.5m ohm.
Another thing to note, 10.000 ohms vs 9.999 ohms can actually be way less than 1m Ohm depending of how the unit rounds off in order to paint the digital display.
Eg; if it rounds up at the 0.5 mark and down when under 0.5, a diff of just 0.0001 ohm (0.1m ohm) could mean a display diff of 10.000 vs 9.999 (1mOhm). That's a 10x differential between measured and displayed.
What if you swap out that 10Ohm DUT with the kelvin current wires to see what the wires ohm in at?