The general thought still debated is that they built the pyramids using a spiral mud brick ramp built around and up on the plain rectangular blocks. The supposed straight ramp would mean far too much debris it would be a pike as big as the pyramid. When they reached the top they started putting blocks on that were smoothed once in place, to the angle of the pyramid itself as they worked their way down removing the ramp. So exactitude at the quarry was not urgent. You can see some of these finished blocks still on the middle pyramid. Similarly the regular big blocks were fitted side by side, the new block shaped to fit the previous one before that one was hauled up.
Current tunneling technique with explosive is to drill central holes that are loaded and blown outward; these are ringed by a spiral of holes loaded with explosive that break the rock into that middle void. Presumably ancient tunneled were as smart. Dig a small hole forward and then break the rock around that hole to expand the diameter of the tunnel. Splitting off rock is a lot easier than digging holes.