I have to agree with you. Maybe the problem is that citypopulation counts agglomerations, rather than cities, and they sure seem to be agglomerating from far and wide. Here, it looks like they've simply counted Brevard and St Lucie counties, including Port St Lucie which is 100 km / 60 miles south of Melbourne. Looking at googlemaps, the whole coastal area in those two counties seems to be an unbroken line of urban-ness.
We've now set up type-ins to accept full spellings of cities where you've been given initial letters. Yes, Frankfurt-am-Main appears in the 10+ letters quiz.
does Frankfurt not make it? or maybe the full name is considered? nice series!