Extremely Misleading, from the studies I've seen these high numbers are percentage of people seeking paternity tests, not from the general public as a whole. If you're seeking a paternity test you already are suspecting infidelity.
The number I've heard from people who quote it is all over the map, sometimes it's 10%, or 20%, even as high as 50%, but I've not once seen a citation of any of them. So I'm inclined to treat that statistic as BS unless proven otherwise. But as you say, even a legit number is probably misleading due to the circumstances surrounding the data gathering.
I have, which is why I brought it up. Any time people throw out such absurdly high numbers and provide "evidence" there always is "...seeking paternity testing..." in the methodology. Always.
It's absurd how people could overlook this, it's like if you counted the times Maury Povich says "you are not the father" and used it to say anything about the general population.