The way i understand it hr usually requires a paper trail before you can fire someone but that paper trail requires the subject to break company policy to earn the reprimand that would make up that paper trail. If someone is just bad at their job and makes poor managerial decisions that isnt exactly a valid reason to fire them so its actually easier to promote them so at least they arent in your department, you can send them somewhere else in the company and make them someone elses problem if you cant find a reason to get rid of them.
Which is a truly unsane policy. How does moving someone out of a smaller group up in the org chart so they now have an even larger surface area to affect sound rational? Move them into the special projects group so they are isolated. Let them study the effect of changing the margin/padding by .5ems to see what happens, and then never implement the changes recommended. Allow them to test which shade of blue makes the users most happy, and then never implement the changes. If you're not going to eliminate dead weight, don't let them drag everyone else down with them.