When viewing a pivot table, the horizontal scroll will lock items in the Rows and only moves the cells. When scrolling the pivot as a dashboard panel this same behavior is not supported.
The row headers should lock when you scroll in dashboard panels.
This also applies to pivot reports and timeline roadmaps. If you have so much information on the right side, the name of the option that you're pivoting on the left disappears when you scroll. See attached where the "Teams Involved" is not visible in my window.