I work as a contractor - mainly to government and my experience is that at least 50% of people in the public sector are there purely to keep people in employment. They serve no useful purpose, and mainly create made up work for each other.
I also do very little that is useful despite bringing a great deal of skill. If they cared to ask me what I think, I would be happy to explain why all the things they get me to do are a waste of time. I’d also be more than happy to suggest some simple things they could do that would actually be useful.
From my own experience, it's not so much about keeping people in employment and more about manager maintaining oversized teams because the size of your team is a status symbol.
Have you considered that you might not have enough visibility into what they do to be able to judge? Obviously the percentage of useless work is >0% but you are just throwing numbers around.
As someone who has worked a bullshit cyber security job in government, I will say 50% is a conservative estimate. Our team had 9 people in it: 1 manager, 6 junior-mid level engineers and 2 senior engineers. The only ones that did any actual work were the senior engineers. The junior-mid engineers literally did nothing for months on end. The manager would disappear all week only to turn up on Friday mornings to give "corporate update" presentations to the team.
I also do very little that is useful despite bringing a great deal of skill. If they cared to ask me what I think, I would be happy to explain why all the things they get me to do are a waste of time. I’d also be more than happy to suggest some simple things they could do that would actually be useful.