This is not just in his book. Every Tozih-ol-massael (resaleh) by Shia ayatollahs include all these topics in the same way.
In fact, none of them have actually written any of these books. These books of fatwa are mostly copies from older books that their students collect, and then the Ayatollah approves it for publication. There are sometimes minor changes as some may have a slightly different fatwa on a topic than others. But the bulk of it is the same, including the table of contents.
Most of these books are, in one way or other, derived from the first book of fatwa written by Molla
Mohammad Hassan Najafi (also known as Saheb-e Javaher, which is his book), a top Sharia scholar who lived more than 150 years ago. After him, major mujtaheds picked up his book and made their own version.
Khomeini's book is called "Tahrir ol Vasileh", which as the title implies, has been copied from "vassileh ol Nejat" which is the book of fatwa of Ayatollah Abulhassan Esfehani a major Shia figu and Marja of early 20th century.
It is interesting that with all their claims to scholarship and knowledge, the two howzeh of Qum and Najaf still do nothing more than copying a book written by a man some 150 years ago!