For sure there are plenty of people that don't produce any real value in their work, but that's been the case since forever and they're hard to weed out because in some ways their full time job is to ensure their ongoing employment.

As in most things, it's a question of extent.

The most accurate statement you can make is that AI will make "most" office employees "more" efficient.

The thing is, this has been happening with every technological advance for hundreds of years.