Hey that's interesting. You have any link on the bold part, I would like to know.
A Principled Stance in Relations with China - Diplomacy | Politics - Japan Echo Web
Maehara Seiji in this paragraph is the foreign minister of Japan at that time.TAHARA On that diplomatic front, in talks with US Secretary of State Hillary Clinton on September 23, you managed to get an American statement that the Senkaku Islands fall within the scope of the Japan-US Security Treaty. It was a big step for the United States to go that far on this topic.
MAEHARA Yes, it was. This time they’ve clearly stated that the Senkakus are under Japanese jurisdiction and are part of the territory covered by the security treaty. The Japanese government has been very heartened by this stance.
US-Japan alliance the big winner from the Senkaku Islands dispute | East Asia Forum
First, the United States has offered reassurance to Japan that the Senkaku Islands fall within the scope of the Japan-US Security Treaty, which obligates the United States to defend Japan. The Japanese press reported an explicit commitment from Secretary of State Hillary Clinton in talks with Foreign Minister Maehara Seiji in New York in September.
The US defense treaty with Philippine is roughly the same, that the US will defend what's currently under Filipino administration, not what's claimed. Thus China triggers an automatic US military response if it makes a play for currently Filipino held territories in the South China Sea.