I think you've missed the point. Even archaeos would spot that not only are they finding only large animals' bones but only the larger bones of these larger animals. Not that I can imagine any kind of soil acidity that would operate with this nice distinction over three thousand years.
But of course on a wider point, the vast array of acid and alkaline soils on offer in all parts of Britain would surely clear the matter up. The finding of particular pig quarter bones rather supports this thesis. Unless perhaps you are suggesting that the acid destroyed all pig bones except these ones, hence leading them to their incorrect deduction.
How I hate defending archaeologists.