Alot of people use terms like that, and not just when they are selling dogs...
If I hunt with someone new or different dogs, i always ask them if their dogs are rough or not..
And you usually get an answer like " he will catch one around 100 pounds "
If you hunt a dog enough and catch enough hogs with them, you will learn about what size hogs they will catch and what they wont...

And if your buying a dog, knowing about what size hog they will catch is one less question you have to ask...