I completely agree, sense motive made zero sense to me. He said it's to find the CR (even when I specified "not how overall strong he is, but how much he is bleeding") and that enemies are basically always trying to conceal how injured they are, even when they're not trying to conceal how injured they are. Including animals (which is what this started with).
Now he's saying that it's carried over from 3.5, which i have never played. I thought he was refeerring to a specific rule and was trying to get him to show it to me, but he kept talking around it. Eventually I got him to admit it (sense motive for damage) was from 3.5 and does not exist in any offical pathfinder source. That it's basically DM fiat. Now, since it's not stated as a specific rule, it's not happening at all.
:/