So does cow milk. 7g* of added sugar in a cup of Oatly, about 8g of various sugars in a cup of milk. Oatly add the sugar to more closely simulate the flavour of milk, but it tastes about as sweet... and both are way too sweet if you ask me.
*The nutrition profile is a bit more complicated as I think they add enzymes to break down starches in the oats, so you end up with more sugar even though it's not technically "added".