cheaters! forming the blocks in place would be like, too easy.
Those blocks were poured and you only need to think about this one for a couple of seconds to grasp the reality that there is no other possibility. Trying to cut literally millions of stone blocks that size would waste most of the stone and there'd be more effort needed just to keep the cutting area clean than for actual cutting.
In real life, you'd fill wagons up with loose stone broken away from the quarry area, haul same in wagons pulled by oxen or elephants to the pyramid build site, pour same into formers as the video shows, add some sort of bonding liquid, and presto, on to the next block. Ever wonder how those blocks fit as tightly as they do? Pouring them would do that....