I think that's largely a myth or at least an exaggeration. I've worked in both Norway and Sweden (and currently live in Sweden) and I've never seen an office party get even close to going way overboard. Office parties in the US and the UK I've seen have been 'worse'.
Sure, but in my experience most of those hookups happen normally and after normal adult interactions, and not as the unintended fallout of an out of control party.
Maybe it's more of a Danish thing but that description is pretty accurate of the parties here: getting blackout drunk and hooking up is bread and butter.