There is a sentence in that article that says “While some theorize that the core is a hot molten ball of liquid, other research indicates that it could be a solid rock 14 to 18 times the mass of the Earth” referring to the core

Would “solid rock” not mean a solid surface in this context?

Sounds like the jury is still out on a solid surface https://www.space.com/18388-what-is-jupiter-made-of.html