Jakarta overtakes Tokyo as largest city, according to UN

I do not like the current definition of Tokyo has being Tokyo Prefecture and all adjacent prefectures. Tokyo itself is made up of wards—each of those considered cities in their own rights—and even a countryside. People living at the far end of Saitama or China can hardly be called Tokyoites. You can't even call someone that lives in China a Tokyoites without being offensive.

is there meaning to the ranking? wouldn't how big a city be be a function of its area? how big before it isnt a city anymore?

is manila a city? chongqing?

is thu duc really a separate city from ho chi minh?

where does bangkok end and nonthaburi start?

Jakarta now has the population of California. It's hard to imagine. What defines 'Jakarta'? How do we say they all are in one city instead of a region, or in several adjacent cities, etc.?