I’ve seen lots and lots of data, probably for years since I joined this website, showing both four and six year grad rates.
Not everyone goes to college full time. People go part time, take gap years or gap semesters, and so forth. I took six years to graduate. I went to CC and transferred. I worked all through college. That is a good way for many people to earn a degree.
Perhaps the data you’ve seen also reflects a trend of people taking longer to complete college. At any rate, I see nothing of real concern. Certainly I don’t think there is any reason to think that providing the six year grad rate “normalizes” something in a negative way.