They probably had a problem with that bolt coming loose. I was told that people do the same thing with the woodruff keys.

You could probably take the clutch assemble off, then use a grinder and cut it off. This way you would have to replace the crank. but the rest of the bottom end will still be usable.

However, if there is no reason to split the cases you could just run it as is until there is a problem needing the cases to be split then worry about it then.