The "Updated" date on the ArcGIS Online item details page should reflect the date the data was updated, rather than the date the item details were updated.
The "Updated" date near the top of the item details page is not necessarily the date the data was last updated. That date can be found on the right side pane, under the Details header, and is called "Data Last Updated." This is the date users care about. They are mislead, for example, if I fix a typo in the item details page, into thinking that's when thedatawas last updated. So, my suggestion is to make the "Updated" date reflect the date thedatawas last updated, or swap the locations of these dates.