"Have you ever noticed the eroded "V" shape in the great step seen in older photos? I have wondered if the portcullis slabs were themselves counterweights that wore it down with use. Perhaps the portcullis slabs as counterweights operated the "pyramid machine" by moving the granite slabs (now wedged permanently at the entrance) and probably slabs that would seal and unseal the queens chamber pathway where those notches are".
Billy beat me to it, but the wear on the Great Step must have a connection to the portcullis system that should be considered. The fact the portcullis door and ante chamber system are there at all, among numerous other things, is reason enough against the tomb theory, so don't get hung up on this as a selling point as it might limit your thinking and only invites nonsense from particular posters that only takes away from the topic at large which is how did they work (and what were they used for).
My thought about the portcullis door system, which struck me when I was there, is that they were meant to be part of a differential system of flow regulation. The raising or lowering of a particular door holds, or holds back, a certain volume and can be adjusted by raising or lowering the other doors which the control mechanism must have been located in the GG. If this is true, looking at your system I would wonder how it would work so that they could be raised and lowered out of sequence without the use of chocks while somehow being connected with the wear on the Great Step. If the bosses were used to hold chocks, I would suggest they were limited to "dry" operation and maintenance.