Finland's total alcohol consumption per capita per year is 12.3 litres. It's the 16th highest in the world. But if Finns drink a lot, then Australians drink a lot, too. According to the same source, Australia's total alcohol consumption per capita per year is 12.2 litres. Portugal is the only country in Europe apart from the former socialist bloc (and Andorra but that could be caused by foreigners buying a lot of alcohol for tax reasons) that has a higher figure.
Yes, the difference is that Australians are likely to have a beer or wine with dinner whereas Finns will get Kalsari Kännissä on a Firday night. :P
It really isn't the volume consumed per year, it is the way it is consumed and, why it is consumed that makes the difference. It is changing in Finland slowly but even still, you won't find many sober Finns comfortably talking at a bar but that is not uncommon in other places.
For many here, they only talk when drunk which is also why there are so many problems. Avoid emotions sober, let it out drunk.
But, I am skewed as I have always been a happy drunk and if depressed, won't ever drink to avoid the feeling.
From a public health perspective, it is the total amount that makes the difference. The amounts of beer consumed in Australia and Finland per capita are nearly equal. One thing to keep in mind is also the distribution of alcohol consumed in the population. From what I've heard (I have no stats at hand now), it's quite lopsided in Finland. Australians do drink a lot of wine while Finns drink more spirits respectively.
Finns as a group are far from being unique in not being very talkative. I visited Stockholm a couple of years ago and went to a few of pubs in hopes of finding people to talk to while drinking my beers. I did and I became Facebook friends with them but those two were the only ones among dozens and dozens of people I scanned looking for people wanting company. The entire Northern Europe is like Finland. Finland is nothing special in this regard. People prefer not to talk to strangers to Northern Europe. They don't talk other people on the train or the bus in London any more than they do in Tampere.