Sorry, I no longer have the save file. To reproduce:
1) Have a pawn with small carry weight / manipulation (e.g., Alcohol withdrawal pawn)
2) Have him butcher a Muffalo on the butcher table.
Receives only 20 meat, while producing plenty of leather.
You need to also have a good cooking skill.
If you go into the pawns info screen, along the left side you will see a list of stats. Look for "Butchering Efficiency" and left click on it. Now in the right pane of that window you will see the breakdown of everything that affects how much meat you get.
Are you sure the leather amount isn't affected in the same way? I'd be surprised if it isn't, but am not sure at all.
Just tested it. Whoops, everything seems to be in order.