I can 100% guarantee you that Probst was talking about Matty's proposal. You can tell from his comments about Matty and Sugar that he loves Matty and isn't that crazy about Sugar. In fact, I would go so far as to bet that Probst cried during the Matty proposal scene and barely even noticed the scene with Sugar and her father's ashes. The show itself also hyped the Matty scene, but didn't hype the Sugar scene at all.