"So why is it that there is such variation in the neck angles on various guitars of the same model?"
Because they're made of wood.
Even when milled on a CNC machine wood parts can shift slightly in dimension - a few degrees either way in temperature or percentage points of humidity can cause very slight changes. And some major "cuts" such as neck "roughs" maybe done months before the parts are actually used.
A very slight dimensional change can result in a more significant change in the angle of fit in some cases. And although parts may be milled on a CNC machine final fitting is done by hand, with "feel" adjustments by the assembler. This is why you'll see different bridge heights (from the guitar top) yet identical action.
It's also why some guitars "feel" better to certain players, or sound slightly different. It'd part of the whole "mojo" of playing wood guitars.
If parts were made of steel...or concrete... they'd all be the same!

Don't worry about it.