...apparently it's not as settled as they thought.
Some scientists are insisting that Pluto should be counted as planet - and their grounds are that Pluto being a planet is common usage. The official definition might say one thing, but the argument being made is that planet is "a culturally defined word that changes over time."
Which really means "Pluto is a planet if you want it to be."
I'm not so sure, but the debate is never, ever going to end, is it.