It's a flip chip design, so the heatspreader and thermal paste does not touch the part that you are seeing in these images. The areas that I think you are refer

It's a flip chip design, so the heatspreader and thermal paste does not touch the part that you are seeing in these images. The areas that I think you are referring to (the big "blob" areas) are computer place and routed standard cells (primarily transistors) that the PNR tool brute forces efficient placement under certain constraints. While it does not produce the most pretty or clean design, it does a good enough job in optimizing for speed and area for most designs.