Is there any reason to separate them out into their own type? They have the same hit dice and Base Attack progression, after all. Are there any giants smaller than Large, or any humanoids larger than Medium-size?
In short, is there any reason not to declare all giants as simply being humanoids, and tweaking references to giants (in the Dwarf's AC bonus, for example), to refer to Large or larger humanoids?
It just seems to me that it's a completely unnecessary type...