First, the Chinese Empire has an enormous geopolitical presence spanning most of Asia and holds the largest population in the world. The Philippine Protectorate, on the other hand, is theme-wise a relatively small corporate protectorate without a lot of geopolitical sway. Tagalog is meant to be a representative of various South-Eastern languages, but sort of ignores the 500lb gorilla that is China.
Second, Chinese culture and influence is fairly prevalent in Withmore (enough that there's a Chinatown) and sees a lot of use in character backgrounds.
I also get the impression that OOCly, its relative obscurity makes Tagalog a bit of an unpopular choice while Mandarin would have more recognition and draw.
Hopefully this would be a relatively minor OOC change that would better represent China's presence in the world, lore and in Withmore itself, giving some scale to the size of their population and their influence abroad.