It's common to see a bunch of hair within a snake's stool also- it's just that we don't always look that close...
I've never dealt with ASF's, that are said to be the normal diet of wild BPs, but I have a hunch that their fur is far less course & thick than the fur of domestic rats- that might be why BPs (or other snakes) seem to have occasional issues with "hairballs"? I do think hairballs are FAR more of a "cat thing" (since they're always licking their fur).
The main concern (IMO) about a snake "coughing up a hairball" is that snake's don't actually cough very well- this was actually a regurgitation, & with any kind of regurge there's always a risk of aspiration into the lungs & of the snake choking to death. Is it possible that domestic rats aren't the ideal food for BPs after all? Domestic mice (which most BPs like) have much thinner hair- they just aren't as large. (for convenient 1-item meals).