This... is... a... BUG.
It worked in previous versions. It is not a feature that I should have to "feel free" to go vote for to get back. Your workaround does nothing practical.
The quick data entry person will tab to the control. They will then attempt to press F4 which is supposed to drop down the list. Did this used to work? Yes. Does it work now? No.
The data entry person may tab to the control and then start hitting the first letter of the item they want to get to the right item. Did this used to work? Yes. Does it work now? No.
I have tried this for the moment in the GotFocus event and it seems to work (this is in VB):
Dim c As Telerik.WinControls.UI.RadDropDownList
If (TypeOf sender Is Telerik.WinControls.UI.RadDropDownList) Then
c = CType(sender, Telerik.WinControls.UI.RadDropDownList)
If (c.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDownList) AndAlso (Not c.DropDownListElement.ContainsFocus) Then
If you think there are negative ramifications to this, please feel free to comment :)