It's hard to imagine he built the tripod just to hide his real method but a few things don't make sense. One, the tripod can only move a stone vertically, it can't move an object into place like a modern crane.

Also the block and tackle he supposedly used are suspect. The picture shows two stationary pulleys. It's questionable with the metallurgy at the time that those pulleys could carry the load. Same with the cables.

Just guessing that his system reduced the force require to lift the blocks by a factor of six, no lets say 10, he would have to apply a force of 1800 pounds to lift the block.

Also I think the upper pulley would have to be ratcheting to hold the load between pulls because you're not going to tie off a steel cable. The ratchet mechanism would be a huge weakness.