The internal cylinder walls are for most part isolated from the outside walls of the block.
I was trying to find a photo of the casting webs that shows the inside look of the block.
You have cylinder walls then a web that ties them to the outside with in between the water jacket.
From as best as I see in the picture the crack is outside and only looks to be outer wall and below the cylinder section.
In addition it is not on the side of the cam shaft is located so no issues there.
These factors minimize the impact to any moving parts and should only have concern with water or maybe oil channels.
