They do explicitly address that - as you yourself quoted above, travelers "... should plan for this dilemma ahead of time", i.e. depending on their personal situation, before the trip they should either be prepared to comply (ensuring beforehand that no incriminating information is accessible and full compliance, if needed, won't endanger themselves or others) or be prepared to refuse and face the consequences; if they believe that they are likely to be inspected for some reasons (the vast majority of travelers are not) then this includes making plans on how to mitigate the effects of not getting across the border.