Recovery mode produces a flashable custom device understood by the flash hardware, and is quite different from a mass storage device (devices accessible as mass storage have programming running to do this…Jetson does not run that programming, it runs something different). What you could do is clone the root partition, edit or clean it up, and then flash re-using the cloned and edited root partition. See:
FYI, if you edit a cloned image from another machine, then the user ID for the case of file additions will be the user and group ID of the user doing the edits (e.g., if on your desktop you edit the image while logged in to user “me”, then the user and group ID are from your host system via numeric ID, and not via name…in the case of chmod or addition of files this can have unexpected permission/ownership changes). Removing files has no effect related to file permissions (no file is created so no ownership or permission is added).
If you have a serial console connected this might be simpler…serial console is always logged in as ubuntu, although you would have to use sudo for some commands (removal of files owned by user ubuntu would not have that requirement). However, if you just need user ubuntu without sudo, it’s already there from very early on, and may work for what you need without cloning or flash.