They don't publish that on their websites, though.
Does X personally post ai generated kids to people's accounts or do people make pictures with a tool and post them on their own accounts?
X is not a person, it is a website run by Elon Musk.
Elon, through his company, publishes the photos. I don't think it matters whether he posted them or not. He was aware of and encouraging of the practice, at least when applied to photos of adults.
Legally, he does not. The poster publishes them onto their own page.