The icons move in a very specific way to accommodate the icons you are moving around.
When you move icons, other icons, need to get out of the way to make room for the icon you are moving. There's no way to move an icon and not have others around it move to make room for it.
If a specific line of icons is already full when you move an icon to it, then the icon closest to the right edge will move to the next line when you drag the new icon over that line, pushing the icons on the next line off by one. Not sure how else you expect it to work? There's has to be room to drop the icon somewhere and if there's no room, then the icons need to move to make room.
If the icons move such that the last line is also full, but needs to accommodate another icon, then yes, the right-most icon on the last line will move to the next page.
Not sure what exactly you expect, if icons don't move then you would have nowhere to drop the icon you are moving.
It can't be static and still accommodate a new icon, if there's no room for it.
You can alleviate this, by having the last space on the last line of every page always be empty. Then moving an icon around will not cause the last icon to move to the next page.
