The blocks are that large as they have been poured in situ. That means the blocks below and beneath create the mould and you only need mostly 2 other walls for a complete mould. That was shown in Davidovit's video. The blocks weren't meant to be moved after pouring.

The 2nd largest building project - measured in stone mass - mankind did after the Great Pyramid was the Hoover Dam (Boulder Dam). That project was build with a similar method: The wall wasn't poured as a monolith, like todays concrete dam constructions, but it was done with in situ block pouring. The blocks were large, about 5m length I guess. This method was used to solve the problem of cooling the concrete during hardening.