A pure metal is never 100% simply because that's practically impossible. Yet the term is perfectly correct when used in the right context. Now that you know it's context dependent you can maybe stop insisting it's wrong.

Pure or ultrapure simply mean different and very clearly defined levels of purity for every field they are used in. Including some that stretch your concept of pure, like pure quantum states. Please don't try to redefine it.

You're going into deeper and deeper mud while trying to walk out clean from this.