P6 7.0 - Customer asking about deleting project codes

Hello, While there is tons of information about adding project codes, I can't find much about deleting them and impacts. My thought is that deleting any existing project codes would result in losing the ability to report on historical projects that used said deleted codes. I have never heard of deleting project codes as being an option. I know we can always add more and edit the description, but that deleting any of them would have a number of potential downstream negative impacts for any projects or layouts that used the "deleted" codes. In essence, that code would just be