I brought this to Telerik's attention 4 years ago. The grid Pager is a poor location for the built-in loading image because it is not clearly visible in a number of scenarios. First off, it is small and tucked in the corner, which makes it hard to see. But there are other scenarios where it is completely invisible. 

If the grid height is fixed and larger than the screen size, the entire pager is not visible unless the user scrolls the window. So, the loading image will not be visible when users take actions like sorting/editing/deleting/filtering which tend to occur towards the top of the grid.

And, if the grid has Paging disabled, then the pager and built-in loading image will NEVER be visible.

I understand that one can add a custom loading image which would work better. And if asked, Telerik can provide a couple dozen lines of custom javascript which will move the loading image for a grid. But If your project has a large number of grids, adding code to each is untenable. And at the end of the day, this should be a built-in feature of Rad Grid, not something that needs to be hacked to work appropriately.

RadWindow used to have a tiny loading image in the status bar which was invisible in a number of scenarios, most notably when the status bar was disabled. The Rad Window team saw fit to move the loading image to the center of the Rad Window where it belonged. This was years ago. For some reason, the Rad Grid team has not seen fit to do the same. Why is the RadWindow team aware of and responsive to concerns about the usability of their control and the Rad Grid team is not?