A temporary visit by a larger fleet may be sufficient. The Pearl Harbor ambush scenario costs IJN its fleet carriers, but not its battleships; if the U.S. sends a large force to the Philippines, the Japanese may decide that sending out the battleships to intercept for the long-planned decisive battle is the way to go. Many did not believe at this point that carriers would be critical to a major fleet engagement, but of course in fact the presence of U.S. carriers and absence of Japanese carriers would make a huge difference, possibly resulting in a near total wipeout of the Japanese battleships as well. And if the IJN has virtually no capital ships at all left, the U.S. doesn't need a very big force at Manila, and can pull back those ships that it can't adequately keep supplied in such a forward position.