The qualification is that even the person doing the job thinks it's bullshit. That doesn't mean the definition relies solely on them thinking it's bullshit.
Frankly, reading through the article, it feels like the definition keeps shifting and much of it is his struggle to even define what it means. He then goes on to start giving his definitions of the what he thinks are types of bullshit jobs.
The article I don't think is all that consistent and shouldn't be taken too seriously.