Connecting Rod Bolt/Nut Choice

I'm new here and have found this site to be a very valuable resource. With that said, I have searched unsuccessfully for an answer to a question I have. Is there any reason to use slotted hex nuts on connecting rod bolts in an engine build/rebuild? For reference, this is a .030 over 360 engine with stock crank/rods making 450+ HP. In the photo, a stock type nut is on the left and a couple of the slotted hex nuts that were removed are on the right. I haven't come across this prior and would like to ensure there is nothing I may be missing. Thanks

Slotted Hex Nuts.jpeg