Of course. What it means is that when you have unlocked the phone for the first time after a reboot, the storage allocated to the main profile aren't encrypted again before you power off or reboot your device.
This is different from the additional user profiles you can create and use. On these profiles the storage are encrypted when you use the "end session" functionality to leave that profile and return to the main profile.
This means that (at least in theory) someone could extract data from flash storage from the main profile if they can manage to get physical access to the storage chip without disconnecting power to it (i.e. turning off the phone). Whether this can be pulled off in practice I don't know.