Two different sides of the card deck:
- apps need the
su
binary to be able to use "root powers"
- the ADB daemon does not; it gains root access while being started by the system in the corresponding mode
The latter is a simple setting in your device's build.prop
file: ro.secure=1
(default on most devices) tells the system to start the daemon in "secure mode", i.e. not with root powers – while ro.secure=0
would turn off that security and run the daemon "as root" – which will be the case with your device.
Knowing that, the claim of being "pre-rooted" is partially true: you can use ADB to "push" the relevant files to your device. Four steps should do it:
adb shell "mount -o remount,rw /system"
adb push su /system/bin/su
adb push superuser.apk /system/app
adb reboot
After that reboot, your device should be "fully rooted" – and "root apps" should find everything they need to work, with you being in control of it via the superuser app.