Its really just about offensive odor in all but the most extreme case's..........in those situations a heavy film of residue can build up and be even more offensive and difficult to clean. As far as actual damage thats harer to pin down and many sellers use the term simply because it has become a mark of care and quality, many audiophiles have pets and kids with no evidence or damage to that affect left behind but they always list no kids or pets.
I have actually been on phone with a seller who put me on hold to let his dog in, another's cat clawed him causing him to let me know his pain and yet anothers dog went crazy when door bell rang, yet all these guys listed no pets.
