Problem is there is ZERO archaeological evidence for iron in egypt at that time.
And certainly not in the quantities required for a pyramid building project.
We must also recognise that all of this occurred at the very beginning of the AE metal age. Most common tools were still stone as seen elsewhere. Stone often being the better choice. Copper being a scarce and precious material used for decorative or status purposes. Stone tools were in common use right into the iron age. We don't find any stone tools in any quantity either.
That's pretty much the "mainstream" archaeological perspective.
If I had the choice between a copper chisel and a flint chisel I'd choose flint every time. Harder, sharper, cheaper, easy to maintain.. disposable..
Flint is forever.. doesn't degrade, but we find no flint chisels in quantity.