Fully groves mains

My 68,
Don't know how many times you have to hear it but slipper brg shells are NOT dead soft. They are made of a springy type of hard steel. Squeeze a shell & it release, it springs back out. Squeezing the same thickness of mild or soft steel & it will bend.
The reason cranks are ground is not because they are 'too hard' for cutting tools. They are ground [ like cam lobes are ] because the smooth fine finish reqd can only be achieved by grinding, then linishing.
A file will also scratch/leave a mark on a crank journal.