They don't care about side armor and active protection (x)The Type-99 was created in preparation for large-scale tank battles and head-to-head tank battles. Therefore its front armor was very thick, side armor was thin
VT-4 developed for export purposes, it has been redesigned to be sleeker, lighter, highly maneuverable and has comprehensive protection on all sides, suitable for urban battles.
China's military doctrine is to avoid bringing tanks into the city, so they don't care about side armor and active protection.
They compensate some protection so that the weight would be around 55tons and the budget would not be too high (√)