I'm just working off context here, can't really defend the Swedes. It seems a little unusual to me too.
But I can't complain too much, because there are plenty of weirdoes in my country who use single dots for time, which I find even worse. Especially because the dot is also often a decimal separator. So depending on context 9.25 can be 09:25 or 9 hours and 15 minutes.
I'm just working off context here, can't really defend the Swedes. It seems a little unusual to me too.
But I can't complain too much, because there are plenty of weirdoes in my country who use single dots for time, which I find even worse. Especially because the dot is also often a decimal separator. So depending on context 9.25 can be 09:25 or 9 hours and 15 minutes.
I like to keep things simple and don't use any separator at all for time.