Images come from folder 'emmc' are used for eMMC installation, can only flash to eMMC storage with USB Flash Tool. Check usage: https://docs.khadas.com/products/sbc/edge1/install-os/install-os-into-emmc-via-usb-tool

Images come from folder 'generic' are used for SD/USB installation, can only flash to TF card/USB Stick. https://docs.khadas.com/products/sbc/edge1/install-os/install-os-into-external-storage