Ok, it appears to be just a local bug- deer and pigs die normally elsewhere, but at the bugged area there were around 15 deer milling around and after killing around a dozen (eventually, took 3-5 arrows each) the place looked like THIS-
View attachment 344993And each of those is a 20 stack of meat or 50 deer hide.
Here's a pillar of the crap dropping from one of my kills-
View attachment 344994
At least 1 boar had the bug too, which was my first encounter with it- looked in my inventory and there were 8 stacks of meat and 2 of scraps.

Havent been back there to check if more have it too. On the other hand, I have so much meat I'm in the process of turning some of it into a couple of stacks of coal for making signs etc because I fucking can!