My intuition tells me there is a gap between the general survey on holiday planning habits and the verification of identity documents.
It smells like a forced link because document verification is primarily an administrative constraint, not a planning option.
For example, in Spain, you do not check your passport "for your holidays" but because the cita previa for renewal is long and unavoidable.
If the survey did not specifically ask about motivations behind this verification, then the link is weak.
It would be more credible if the study proved that respondents directly associate holiday planning with anticipation of administrative procedures.