You're quite right actually; if the inscription was made vertically in situ then one would not expect the orientation of the glyphs to be as they are.
I assume this is why Egyptologists have claimed it is a quarry mark that was inscribed horizontally once the block had been quarried but before it ended up being positioned 90 degrees clockwise once it was positioned on the GP.
I find it unlikely that the workers were able to read and write hieroglyphs. The British museum website states: "In Ancient Egypt literacy rates were very low, less than one per cent."
If this is the case - and given the fact that the GP is free from any hieroglyphic inscriptions such as the texts which adorned tombs of later dynasties - the question which no-one seems to be asking is: is it reasonable to assume that a labourer would even know how to write the hieroglyphic phrase daubed in the relieving chamber?
Just a thought.
Post Edited (15-Jul-14 22:00)