Didn’t Pluto get its planet status restored? So shouldn’t this be Planet Ten?
(Ironically, 10 in Roman numerals is X. so that would make this the famous Planet X.)
So maybe Pluto was upgraded from "dwarf planet" to "unofficial planet."
No. Look at the diagram in this video. Planet X is the green orbit labeled FE72.
https://www.youtube.com/watch?v=Og1MBx78NKs