The country is not monolithic. It could be considered typical, yet you might still have only 70% being two income households.
It would be silly to include the other 30% as unemployed.
That being said, "seeking employment" is likely one of the worse indications of unemployment. People may be excluded or impeded from joining the workforce for a variety of reasons and stop seeking employment because of that. It is a rather long list: discrimination (age, disability, gender, race), accommodations for disabilities, access to affordable childcare, criminal record, level of education. While some of those can be addressed, they rarely are addressed in a meaningful manner. In those cases I find it difficult to treat not-seeking employment as a choice.
Another route, similar to the one in this study, may be considering people who are actively searching for work and where the household income is below a certain threshold (likely based upon the composition of the family).