G=m/s
The results of this exercise appear to confirm your conclusion in that paper.
I am amazed by how close they agree with those of the full one-port cal and
that of your mini-equation.
That works when short and open results are similar and load signal is small.
Small load signal is generally easy for resistance bridge at low frequencies,
not so much for reflection bridge and higher frequencies.
Open = short works better for nearly no distance from bridge to DUT,
not so well for real cables of some length.
Oristo