As above, It's been ground for a purpose of probably better purchase in a holder with a grub screw and quicker tool change time (possibly)
No one can categorically know as millions of tools are ground and altered for a purpose, unless you are the person that did it, its going to be guess work what was in the persons mind as to the reasons. You see a lot asking about purpose ground and modified tools and 'what is it'
No one knows exactly unless they are the person that did it. Special purpose tools for a reason.