Starting to sound like iPhone X sales really are falling short of expectations.
He is referring to this report by Bloomberg. There have been other reports and rumors too but this one seems legit.
I have no idea if the iPhone X is selling well or not. I have only seen a few of them in the wild (probably 3?) so anecdotal evidence says that people with iPhones 6 or 7 or 8 are loving their phones so much they don't see the need to update yet.
I can also say that Eliza has an iPhone X and hates it. And I do mean hates it. She complains about some detail of it at least once a week. She loved all of her other iPhones. If she had her choice right now she'd prefer an iPhone 8. I'm going to try to see if she'll jump to the Pixel 3 with me when it comes out but I won't hold my breath.