I think you are referring to what is mentioned here: eesdr.com/en/software-en/bug-report A specific operation of the antenna switch, when there is one ADC and two software RXs.
Since there is one ADC, both RXs use the same ANT input, that is why when you use RXs on different bands, you still use one ANT input for both of them.
When you switch the RX1 (main) to the other band, ANT input is also changing for the RX2, example:
You operate on the 40M band, using both RX1 and RX2 on ANT3 input. Then you move the RX1 to the 80M band, which was set up for ANT2, thus both RX1 and RX2 switch to ANT2 input.
We know that it is not the most convenient way to operate two software RXs, we'll try to make it more comfortable in the ESDR3.