A brief scanning of relevant information seems to indicate that Egyptologists starting with the famous Flinders Petrie haven't considered this matter to be any greatly important mystery.
I think the importance - and method used has been overlooked and simple answers assumed.
For example. If the 3 blocks were designed so perfectly to fit by wedge fit, it would be be difficult to try this out during the construction - without getting them stuck in the first place. So they were designed and set in the open position for some time before being slid into place.
Second, the angle of the slope is such that it would not require people to move them at all - just gravity. All that is required is the release mechanism and somewhere to store them out of the way prior to being released.
Virtually everyone so far has said that they would reside in the ascending passageway, and the workmen would have to clamber over them all the time, but nobody yet as far as I know has investigated that they may have sat inside each of the 3 girdle stones along that shaft, and that the girdle stones are themselves containing 2 voids and able to be raised.
Think of it as a figure 8, the lower hole is empty and initially lined up with the passageway. The upper portion is within the structure out of the way, but contains a blocking stone. In the upper position this girdle stone provides a free passage, but when triggered it will descend, and at the lower point the blocking stone would line up with the passageway and be released to slide down into position to block the passage.
My main question is when it was released and blocked. Did the Pyramid function until it was blocked, or was it blocked and continued to function, until that robbing tunnel was dug. I suggest it was intended to function after it was sealed, and the upper portion was intended to be airtight.
So if nobody had to be inside when it was sealed - there would not need to be a bypass route at all. Just making one would end up being common knowledge to the builders, and it didn't have any such security on it.
I realised something else about how it was sealed. It's to do with the insect frass found in the area above the kings chamber. Lots of insects - but the archaeologists don't know why?
They also found a type of salt known as natron. When heated this looses it's water of crystallisation and then becomes an effective desiccant.
I believe they did something very clever here and that is to fill the chambers above the kings chamber with corn meal containing insect larvae, and in other areas of the structure place the desiccant. Then seal it.
This way- first the oxygen would be used up by the insects first hatching, breeding and living in that area - until they all died off from lack of oxygen, then the desiccant would remove and hold the moisture leaving it an area free of moisture and oxygen. - An ideal place for preservation.
Today we still use desiccants and oxygen absorbers in food preservation and equipment cases that are sealed.