The phrase "disappointing facts" is correct and usable in written English.
You would use it to describe facts that are not what you expected or wanted them to be. For example, "The research revealed some disappointing facts about the company's financial situation."
Moreover, through our field observations and investigation from the local health bureau, we found there existed a lot of disappointing facts regarding the so-called private clinics, including unsanitary conditions in medical facilities and a lack of modern medical equipment.
Just as with the repulsive internet meme 12 Extremely Disappointing Facts About Popular Music, it's accepted that music created by women or consumed by women is inferior.
Then, you must take into account the disappointing fact that women, on average, are never paid as much as men.
The disappointing fact is that the rate at which the fund has been expanding its work will be greatly slowed.
One disappointing fact is that this book trivialises important historical events and turns them into a parody.
It is a disappointing fact that there remains a huge gulf in the university participation of pupils depending on their background or the school they went to.
I suppose the one disappointing fact was that he wasn't here to see me play for England but I am sure he is looking down and very proud.
This is a disappointing fact, but it does not cancel out the ingenuity shown by the soldiers, many of them only in their twenties, who have ethically managed budgets equivalent to that of a small town or medium-sized business.
"But the disappointing fact here is a complete lack of any understanding of what's required for education," he said, pointing out that members of the United Federation of Teachers had seen four years of school budget cuts and get "no support" from the Education Department other than "more directives".
"That's the disappointing fact, that we didn't score.
The one disappointing fact is that total consumption of civilian aviation fuel has gone up and up, too.
