If it were the ancient’s intent to communicate the age of the pyramids by designating a particular configuration of star positions correlating to permanent structures on the ground, then reversing the positions of the pyramids is not helping. Reversing the layout only distracts from the main purpose, so that’s the first reason it doesn’t seem to substantiate the theory to me. Any of the rationale’s for the reversal aren’t convincing to me in light of the presumption of their intended goal.
Secondly, why use the extrapolated measurement of 'one angle' to be the sole indication of that age, when you have the opportunity to make an actual alignment of stars and structures to pin point a date based on a more direct and observable correlation.
What would inspire me to jump on the bandwagon of a theory would be for it to tick more boxes. It would have to be both functional in determining and communicating a particular point in time from the star/structure alignment, but also be intuitive and relatively simple and clear in the way it achieved that. The presumption is that they wanted people to figure it out as easily as possible to maximize the chances of success of communicating something across millennia.
It would be more intriguing and believable if there was an actual alignment implication when Orion lines up with the pyramids when they are on the opposite side of the earth. If the pyramids are on the face of the earth facing 180 degrees away from Orion, if you project lines through the earth towards Orion, its possible there is a point in time when Orion lines up perfectly with the pyramids with all 3 points and angles matching perfectly with no reversal necessary.
And even easier than that, if both triangular formations, Orion and the pyramids, were intended only to designate a projection based on the line joining both triangles’ centre points, it wouldn’t require the excessive precision of having to match angles exactly to make a determination. Further, if that projection has only one point in time during each precession, that it projects through something obvious like the Sun, then I’d be really intrigued.