Finland has 230V, so if you're from the US with 110V the low current rating might be confusing ;-) I'd also guess that in Finland they also run three phases into each house/unit (we do in Germany), meaning that's 3*63A = 189A. (Or just shy of 400A on a 110V grid). For us that's the default grid connection you get for your house.
As for your guess: That's just a cultural thing I suppose. I've never seen outdoor meters around here.
The US is 240 volt for power purposes. The 120 volt thing is just dividing that in half - the meters don't measure that. These days most US houses get 200 amp service, but in the past 30, 60, and 100 were all common (100 is still done). I know of a few houses with more than that, but those are not normal.
3 phase is different from us split phase. In the us that would be 404 volts (or about that, I don't work with it just know it exists) or 208 volt if you that the split phase in 3 phase.
Anyway the point is 3 phase is not added in the same way as split phase. I think you know that, but I'm sure someone else doesn't.
Naw, Canadian. Cool to have 3ph at home (even without the #1 thing that fails here because we don’t have 3ph: a/c (capacitors)), but why’s your industrial supply just 400V instead of a soup of 347V, 480V and 600V?
As for your guess: That's just a cultural thing I suppose. I've never seen outdoor meters around here.