BTW 16-11th c BC is after 2500 BC
Only about 1100 years...
My point is that they were built way before copper.
Long before the Great Pyramid was built, Egypt already was using, and (of necessity) trading, copper. They were using some copper in the pre-Dynastic age by 4000BC, and possibly closer to 5000BC. (The earliest known use is around 5500BC in south-eastern Europe. It spread pretty rapidly.)
By the time the Great Pyramid was built they had already had bronze for centuries (although not in large quantities, it was not common until the 18th Dynasty) - the First Dynasty corresponds roughly with the start of the actual use of bronze in Egypt and the Great Pyramid wasn't built until the 4th Dynasty.
I recall seeing something that indicated that they used copper chisels when building the pyramids mainly because a bronze chisel that gets dull is a lot harder to resharpen than a copper chisel and a lot more difficult and expensive to make in the first place (especially since there was no significant source of copper in Egypt, let alone tin). Once they wear too much you have to melt them down to make new chisels and that is a lot easier to do with copper than bronze. They used a lot of chisels when building a pyramid. So even though the cooper chisels went dull much quicker, it was still more practical to use them.
By the way, Imhotep (apparent inventor of the Egyptian pyramids, and possibly the inventor of the stone column in architecture) had as one of his titles "Chief Sculptor". The Egyptians, and other early cultures, were producing very good sculptures before the pyramids were built.
I'm not sure what my point is, except perhaps that producing the pyramids before Bronze Working (and Sculpture) is earlier than it was done in the real world. Doing it before Copper Working is much too early.
Around the time they were building the Great Pyramid is when they invented the first known synthetic pigment, Egyptian Blue is what it is called these days (it is one of the few post stone-age technologies that has ever been lost - it disappeared shortly after the end of the Roman Empire and was not reinvented until the 1800s), and one of its key ingredients is copper. Copper was also used to color Egyptian faience (a type of ceramic) before that. So not only did they use copper directly at that time, they knew how to make other compounds out of it.
