No, actually, the real problem here is when you try to scroll within the same page of data.
1-The current scroll position loads item 200 to 299
2- Usually, the grid's height will allow you to display only a part of those rows so let say that rows 230 to 239 are visibile.
If you want to scroll down to row 240 from there (using the row's top position), you will have to call the verticalScrollbar scrollTop function and this is where the problems starts.
If the prefetch is enable (default value): the grid will simply scroll to the row 240 without triggering anything else. That's the expected behavior (but the prefetch is causing the slider issue I pointed out in this post)
If the prefetch is disable: the grid will scroll to the row 240 AND trigger the grid dataBound callback. It's not necessary to trigger the callback at this point since the grid has already loaded all the data to be displayed. Triggering the dataBound callback have a real impact on the grid performance, especially when you want you need to navigate within the grid.