Because giving the impressing that LGBT issues are an imposition on Chinese society by the West in general and America specifically is going to distort the issue at best and at worst give the conservatives ammo to say that LGBT is an American plot to blah blah blah. Especially in the context of a Disney movie, aimed at kids, which adds in a “they’re coming for our children” factor.
It would do incalculable damage to the advancement of LGBT rights in China for such rights to be tied to America or the West, so on balance the censors probably did the LGBT community a solid here.
Plus, that’s assuming that this is the censors in China and not Disney self censoring because Disney thinks the Chinese censors care.