I don't really see how it can be described as anything other than a "home made approach" given that they descended out of whatever FL at which they had been cruising, and tried to fly what they thought was a straight in approach to an airport with no IAP in at best very marginal VMC. After all: if they really could see the airport, how did they come to be victims of CFIT?
That's not the same as an "unpublished letdown". It sounds like that crew were attempting to fly VFR in IMC, which is a totally different thing.