I haven’t been able to test yet but it looks like the same issue exists. Cboot isn’t enumerating the mass storage devices properly. It’s finding the hubs and testing them for mass storage which of course will fail. It never goes on to the connected devices to find the actual USB mass storage devices that may be connected to the hub.
So it looks like you still need to have the APP partition on the sdcard or emmc.
Having said that you do not need to have the rootfs partition on the sdcard or emmc. The APP partition only needs to have the /boot directory on it not the whole root filesystem. What I do is to have a basic root filesystem on the sdcard/emmc and have the /boot/extlinux/extlinux.conf APPEND line use root=/dev/sda1 where sda1 is the real root partition on a USB stick (or nvme or whatever) then in /etc/fstab mount /dev/mmcblk0p1 on /boot.
You can even create additional entries in extlinux.conf to allow you to easily switch between the rootfs on the emmc and the rootfs on the USB device.