Forming Malaya?

[Trin Tragula]

It requires all provinces that are part of the island areas. This means you have to control some of the islands of the coast, see the area map mode to find which ones.
For it to count Java you need all provinces belonging to the areas of Java, for it to count Sumatra you need all the provinces belonging to the areas of Sumatra, and so on

 

[Trin Tragula]

The wiki is simply incorrect (as is often the case when the game is updated).
Follow the instructions I gave you and you'll be able to form Malaya. I tested it before posting to be sure.

So far, nobody has agreed with my contention that this might be a bug, but neither has anybody offered any other explanation. Is there anyone at Paradox who could check this out?

I did and I already replied did you try what I told you? If it still doesn't work you may have a bug and should post the game in the bug forum
As the current tooltips seem to cause confusion I'll try to update them to be more clear. The fact that the game doesn't follow wiki is not a bug though as that relies on players to update it.