Quad tree is pointless for tile maps
A QuadTree excels with many static objects that don't move. A tile map is literally
perfect for a QuadTree. Even if he's clumping his tiles into giant objects, something he probably shouldn't be doing, a QuadTree would still heavily reduce the amount the draw calls.
and he want's to have full zoom out anyway.
That has
nothing to do with spatial indexing. If he wants to zoom all the way, fine, a QuadTree won't help when he's drawing every entity on screen. But for the mast majority of applications you're not zoomed all the way out.
Hapax hit this problem on the head and a QuadTree would be the way to do what he suggested.
"Why are you drawing all 256 chunks that are each 2048x2048?
Surely you only need to draw the one(s) that are actually visible."