It looks like this frame name never existed in Blizzard. I went back to 8.0.1 and the world map xml hasn't changed. Maybe it is something in Titan Panel. A quick google for the frame name came up with only Titan Panel related comments.
Correction:
It looks like the world map has been changed enough that the name and functionality is different from what it was in 9.0.1 ..
The actual xml with those frames in is
https://www.townlong-yak.com/framexm...taProvider.xml
And this template is used in the lua file... and the reason it can't find the frame ? The frame that uses it isn't named.
https://www.townlong-yak.com/framexm...Provider.lua#8
And this appears to be where the World Map adds the data provider for the labels.
https://www.townlong-yak.com/framexm...rldMap.lua#162
First guess ( as I haven't played with map stuff ) is that you need to see if WorldMapFrame.Label returns the same info as the old WorldMapFrameAreaLabel did. The rest of the information is in the first xml file I linked as keys .. so Label.Name and Label.Description. The question is whether self is referencing the WorldMapFrame or not.