The UI behaivor of drag selection shows inconsistent behavior between WinForm vs WPF/Excel.
When you drag some cells for selection and keep dragging to the right (getting the out scope), the control scrolls to the right.
This behavior is common in Winform/WPF/Excel.
When you drag backward (to the left), WPF controls scroll back and so is Excel, while Winform controls does not scroll
Same thing for top and bottom scroll. Winform Spreadsheet control does not scroll. It may scrolls only to the right.
Another Caveat I see meanwhile is that when you scroll backwards until the row area, the pointer become row-resize pointer, or so
If you keep mouse moving around, it sometimes makes a horizontal line (possibly a guide for row resize?)
The issue in this case is that, it does not remove itself. the horizontal line stays there. It is not very annoying (as it is thin horizontal line) but is still a bug.
create a empty Winform app, with the RadSpreadsheet Control, and Run
Drag from row C3 and to the right (around the scrollbar) the control scrolls to the right (this is not quite smooth though..)
Scroll right to AZ3 say, and drag backward back to C3, this now does not scroll back.
Same for top and bottom.
Do the same for WPF, it now works as expected
Do the same for MS Excel, it now works as expected.