Accurately measuring 1 mill-ohm is difficult indeed!! How good is the repeatability??
With a 10ma source current the DUT voltage is only 10uV, and why the Bench type LCR meters utilize much higher currents (some > 0.1a rms). Maybe a good zero ohm calibration can remove effects as the DUT current must be limited to something practical with a small battery powered handheld tweezer. Recall that some of low cost battery powered Milliohm meters source up to 0.2a DUT test current, but they also use a large 18650 battery.
BTW the GS8632 isn't that impressive an op-amp with 3.5mV offset and 2.4uV/C drift, the INA826 isn't that outstanding either, however one must consider the product cost target!!
Anyway, curious as how well these tweezers perform with low milli-ohm impedances. Maybe they have some clever design tricks that make this repeatable and accurate, detailed testing against known good references should show the performance.
We are temped just to "see"
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Best,