This is such a funny comment because it’s both right and oh so wrong.
Yes, the U.S. was likely never gonna send troops to fight in Taiwan (although it has sent troops to fight in Korea, so it’s not as much of a stretch as you claim).
But the bluff worked because the U.S.’s promises held value. To the point that the U.S. didn’t explicitly say they would defend Taiwan against China, but China was avoiding confrontation with Taiwan simply to prevent the U.S. from saying they would do that.
Of course, Donald Trump damaged that significantly in his first term and has torn that to shreds in his second term.
With Trump’s nakedly transparent and quod pro quo based foreign affairs, it’s hard to remember how much soft power value the U.S. had built up over decades where it could achieve what it wanted without even saying anything, which has basically been destroyed over about a decade.