Modern XCO courses are pretty technical, so they gamble whether that dropper will save more seconds on the downhill than any weight saving saved on the uphill.
They have to make the same decision between using a hardtail or full suss for a particular course too.
Lighter would be to not have a dropper post, especially one that only moves 35mm.
I've never used a dropper so he obviously feels that's enough droppage.