is Indonesia a modern day empire pretending to be a country?

[Lord Halifax]

Not really, no more so than India or Philippines who have multiple languages and ethnic groups.  

Is India?

Is Papua New Guinea?

Is any multicultural country with a strong central government?

Indonesia has settled millions of Javanese settlers on other (thinly populated) islands, which arguably amounts to internal colonization. Neither India, the Philippines nor PNG have done that.

China would be a better comparison, since they've actively settled Han Chinese in ethnic minority dominated regions.

[Lord Halifax]

Not really, no more so than India or Philippines who have multiple languages and ethnic groups.  

Is India?

Is Papua New Guinea?

Is any multicultural country with a strong central government?

Indonesia has settled millions of Javanese settlers on other (thinly populated) islands, which arguably amounts to internal colonization. Neither India, the Philippines nor PNG have done that.

China would be a better comparison, since they've actively settled Han Chinese in ethnic minority dominated regions.

Apples and oranges. China and Indonesia's actions are driven by fundamentally different histories and the cultural fault lines are significantly different. Population demography is also sizably different. (There are no places in China as singularly dominant with such small a slice of the broader land area as Java is in Indonesia, and Javanese are not that much more 1/3 of the overall Indonesian population - a far cry from the overwhelming Han Chinese majority in China. Han Chinese is also more purely a cultural grouping than an ethnic category tbh)

The point was not that the situation was identical, but that it was a better comparison than to India, the Philippines or the other countries mentioned since China has actively engaged in internal colonization while they haven't.

The extent of countries like China and Russia is the result of internal colonization so it's not an "apples to oranges" comparison despite all the differences. Indonesia is at times called a "Javanese Empire" because its development since independence has some similarities to other big countries based on one ethnic group expanding outwards from a core area and creating an empire like Russia and China (or for that matter Persia and Ethiopia, though they're both more "oranges" in this context due to less settlement). That's the whole basis for the concept.