An obvious explanation would be that this helps distinguish it from øØ (as in Danish and Norwegian), which is slashed from bottom left to top right. The Wikipedia article does demonstrate its legibility when blurred.
interesting way to describe this in that it is described in reverse order of how i've always seen it. my first thought is that's because it is also opposite of how i would draw it when writing by hand.
I honestly don't know the stroke order Scandinavian kids are taught when learning an alphabet that contains the letter. I also don't know if it's consistent across languages.
Most strokes that start from a lifted position move from left to right (e.g. the crossbar of the lowercase t) and European languages are written left to right, so describing it as left-to-right seems more intuitive to me.