I know nothing about commuting in Finland but is Uusimaa not roughly equivalent to "the economic gravity well of Helsinki"?
Sounds like you two are nit picking over the difference between the I495 loop being the "DC area" vs everything east of Fredricksburg/Front Royal/Fredreick being the "DC area".
I've no idea of the Geography you are referring to in the DC area, being European. That said Uusimaa is a region, Helsinki is a (capital city). Helsinki spans quite a large geographic area and is fairly densely populated but primarily in a metropolitan area. Take a look on google maps and you'll see it's tiny, say compared to London, Paris, Berlin etc. Uusimaa covers a much bigger area with huge amounts of space between the edge and the metropolitan area (mostly covered with fields, private land and forest).