Hi Stockie.
I don't know the answer to your first question but maybe have a clue for the second :
Diddle phrase only uses the tip of the tongue to move in the front of your mouth (right behind the front teeth) > D-D-L
Wheras Drong also starts with a tongue-tip-in-teeth position (D), then moves to the retroflex position of the tongue (R-oN), and finally, the G sound is guttural (back of throat).
This tongue and throat movement enables you to do a quick "tongue-breathing", unlike Diddle.
To my ears, Drong is closer to Dhrill than to Diddle...
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