My point was that you need to understand that the "scanner" is not and never was intended to be searching ports on the MCU chip which as you have gathered by now, would be quite inappropriate not only because the hardware I2C subsystem is fixed to certain ports, but as you clearly know which ports these are and to which you have deliberately connected your I2C device.
The "scanner" is helping you to find the things you do not (necessarily) know, the "invisible" address inside your I2C device which is not a physically observable object. The "guesser" is determining something which you could figure out by carefully examining and testing the traces on the "backpack", but is rather inconvenient to do so.