For me, it may be that the toilet paper roll needs to have the open end away from the wall. I don’t want to reach under the roll to take a piece! That’s ludicrous!
That or my recent addiction to correcting people when they use “less” when they should use “fewer”
But once they put stuff in it, displacing the air it’s initially filled with, that stuff is indeed concrete (aggregate + cement + water), not just cement.