Avalo's arm is the size of a neighbourhood. You can literally see houses attached to it. TB is an actual island.
Nah, in later panels you can even see the hand touching the skull and how large it is in comparison. If that's the size of a neighbourhood, what is TB then?
Plus, taking buildings into this equation when Oda has different sizes for buildings in One Piece (ie Onigashima) is misleading the fact that an island larger than TB just formed entire large limps.
Edit:
Again, how are these arms smaller than TB? It's like Onigashima suddenly creating wide arms of which its hands are comparable to the skull.