That's similar to UK, many people think they've seen UK because they've been to London but there is a lot more outside of London as well. Though I think, the balance between London vs the rest of the UK, and Oslo vs the rest of Norway is quite different as things are quite heavily focused in London. Whereas from my limited undestanding, Norway seems to be very famous for its fjords and the rest of the country which seems so beautiful.

I would love to go back to Norway again, as I think I have hardly scratched the surface during my flash trip to each location.