They're building a showcase city a thousand kilometers away in a different island as the new capital, but they're not relocating the 20+ million who live in Jakarta.
They are relocating the government. The private companies weren’t invited. This is like how Burma moved its capital from Rangoon to Nay Pyi Taw, Rangoon is still the commercial capital if Burma.
The other examples I would reach for are Côte d'Ivoire moving its capital from Abidjan to Yamoussoukro in 1983, or Nigeria moving from Lagos to Abuja in 1991. In both cases, the old capital is still far and away the largest city in the country, like 10× the new capital city.