Assuming the 5% statistic is accurate (bold assumption but I'll roll with it) we could say that perceived higher ratio is a result to mixed-race couples being more publicly performative, and possibly a result of it being more common than average where you live (and where I live, and where other people who have testified a higher frequency live as well).

Naturally I don't find it compelling that it would account for such a discrepancy between the commonly given statistic and observed reality.