[Synchro909]

Although that is not my favourite way of doing it, I've seen bearings like that go for a long time. It is clear that those are not new bearings and that they haven't been a problem so far. The oil flows around the bearing through that groove till it gets to the join between the block and the cap. You'll notice the edges there are chamfered almost right across the bearing. The oil runs along there so you have lubrication right across the bearing surface. More oil on one side than the other but adequate.
That's fine on the front and middle bearing but I like a spiral groove in the rear one to get the oil across the bearing better.
You can add the groove in the top half now if you like.