This did not work for me on Catalina. I updated /opt/scripts/ and saw your changes in boot/am335x_evm.sh. In /etc/default/bb-boot I tried USB_NETWORK_RNDIS_DISABLED=yes and no network interface was shown when I did an ifconfig except for my ethernet connection (I’m connecting over ssh through ethernet). I also tried USB_NETWORK_CDC_DISABLED=yes and the usb0 network interface shows up when I ssh in over ethernet, but still doesn’t connect from Catalina over usb (but does from High Sierra).
Can you try disabling CDC, leaving RNDIS enabled and install the HoRNDIS driver?