"drew itself to a great height, and its wings spread from wall to wall"
But before the line you mention it says:
“His enemy halted again, facing him, and the shadow about it
reached out LIKE two vast wings.”
Hence the great flame war! The main arguments for both sides can be seen at http://tolkien.slimy.com/ , under the “Creatures’ Characteristics” section. You can also follow the debates over the great issues of of our time such as, “Did Dwarf women have beards?”