I am sorry vk, in a vain attempt to be overly cute I might have mischaracterized the rAga durvanki. I don't know about its antiquity, I am sure keerti can write a thesis on it as on all other CM topics (and it appears, chemistry, etc...), but it certainly has a bonafide identity and a "right to exist" in my reckoning ! The raga has a distinctive dhaivata and emphasizes MPD sequence in the arOhana in a way that none of the "related" ragas (strictly in terms of scale) do (Suddhasaveri, arabhi, etc..). In that sense it is vaguely reminiscent of kunthalavarali for that brief window.
There is only one song, Gam Ganapathe by Jayachamarajendra Wodeyaar which R K Srikanatan is the only one known to sing. Even if JW "created" it, it is a good creation and now has a life of its own, waiting to be explored.