I just tested this in a virtual device and you can see the behavior in the attached video. The device overrides the usual dropdown behavior of desktop browsers and shows a dialog that covers the screen and it seems to block the execution and then immediately initiates the postback. There simply isn't a way for the RadToolTIP to show. Nevertheless, thsi behavior was not observed when clicking on the arrow of the dropdown, yet this is hardly possible when using your fingers and an actual device. All this means that there isn't anything we can do to change this because this is how the browser and OS handle dropdown lists.
the Telerik team
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