In this article here:
However, I don't understand the rather critical line "instead of looking at the voltage on the output of the amplifier, switch, Switch S2 connectsthe output of the circuit directly to the gain resistor. This eliminates any gain errors due to current flowing through Switch S1."
What exactly is it trying to say here? Because I don't understand what it's trying to do with that second switch. The same resistance is still in the feedback loop, and the same currents flowing in the feedback loop still flow through the switch. All the second switch seems to do is isolate the unused feedback path even more, but that doesn't seem to be the intention.