At the moment, UART config is still fairly limited through libdaisy (i.e. only the primary UART1 is implemented).
When we get around to adding the multi-peripheral support (like in I2C, etc.) you will be able to use either pin for UART1 Rx. The STM32 has many alternate functions for various pins, and there are several that overlap to allow for more flexibility when desigining hardware.
This will be fairly transparent through libdaisy. You’ll be able to pass either pin to the config struct, and it will automagically assign the correct alternate function configuration, etc. for that pin.