ok, there are two different fastboots. the userspace fastboot, fastbootd, can look inside the super partition. when this one is running, there is a graphical menu on the phone saying "fastbootd" and `fastboot getvar is-userspace` returns "yes". the simpler one doesn't look inside super and returns "no". i got into fastbootd by booting into android then doing `adb reboot fastboot` .
there are also tools to extract/repack the super partition off the phone.
