How do we know "the wrong checkbox being selected" was a Preview problem and not something to do with non-standard PDF construction ? Also, I don't know about

How do we know "the wrong checkbox being selected" was a Preview problem and not something to do with non-standard PDF construction ? Also, I don't know about you, but AFAIK pretty much all software these days (whether closed-source or open) comes with a great big disclaimer attached effectively saying "you're on your own" if the software functions in an unexpected manner.