Commons Clause does not meet OSI's definition of "Open Source" nor the GNU/FSF definition of "Free Software" so it's fair to say it should not be called either.
Yes, it doesn't fit either definition, so it shouldn't be called either.
The term 'free software' is hard to keep 'pure', because it has an obvious meaning for people who know nothing about software licensing.
But IMO, the terms 'libre software' and 'open source' should not be diluted. It doesn't serve any purpose to mis-use those terms, except confusing everyone.
Prescriptivism is a policy you can choose to follow, but I don't subscribe to it. I'm a descriptivist through and through. And from what I understand, I'm not the only one.
The very language I'm writing this to you in is probably the world's most exemplary instance of this principle in action.
Besides, isn't using things in other ways than they were originally intended the essence of The Hacker? ;)
If you're not going by their definition, I think you're just wrong.