As the titles says, you can try it for your self in your own demo, http://demos.telerik.com/kendo-ui/grid/editing-popup with an IPad.
Open the popup for editing and you can still scroll the grid in the background. You can also try to move the popup, but instead you scroll the grid.
This is a big problem if the modal window is so big that you have to move/scroll the window. If you try to do that you only scroll the grid behind the modal window and everything seems stuck...