I don't disagree, but I think part of the reason they can say that is that it has not been exhaustively studied. There are various articles on nih.gov [1] that summarize the problem and what would be required to properly study this. There is also a big monetary advantage to using antibiotics in animals which makes me skeptical of any documentation. Perhaps I am too skeptical.

[1] - https://www.ncbi.nlm.nih.gov/books/NBK216502/