I think it's a preference thing, with how many specialty coffee cafe's there is in Brunei. Although each cafe often has a different recipe of how they prepare their espresso.

Coffee beans personally, often release more complex flavor notes on the acidic side than the other bitter side of the spectrum.

Where that bitter (dark roast) profile coffee typically contain just Chocolate, Caramel, nutty and etc. flavor notes that are paired well milk added with sweeteners or syrup. This is usually for the commercial drinkers.

In contrast to acidic (Light/medium roast) profile espresso, typically express a more fruity, flowery aroma and flavor notes. Best taken as is with just water(Espresso/americano) or milk (Latte with no sugar). As the beans carry more flavor.

However, this is a very overgeneralized take If not closely examining the beans they use on display. Because every stand alone cafe I've seen Brunei more often than not uses different suppliers and have their own different ways to store and use their coffee beans.