The reason I suggested it is that, that test/that idea is essentially the root of all rating systems/standards.
Zone system users often shoot at 1/2 box speed, IMO that is mostly a style bias, detail in the deep shadows is really important to people who enjoy the "west coast style". Absolutely nothing wrong with that, the ISO is still the same, the EI is simply adjusted to allow easier printing of their style.
Personally, I don't care as much about the deep shadows, I care more about shutter speed to control motion blur, my subject matter/style/sensibility are different from their's, so my EI is different.
You have to test, formally or informally, to find what EI works for you.