Yes, that's right. Second study publication at one time could be any 192-page book. Then they came out with United In Worship of the Only True God. This became the required second study publication (unless the conductor strongly felt another pub would serve better). Now they have Worship the Only True God as the second study pub.
Interestingly, the Bible Teach book does not contain any reference to the Faithful and Discreet Slave. Worship God waits until chapter 10 to spring this beauty of a false doctrine, and waits until chapter 14 to explain it. The student would typically be baptized before ever learning that they have signed over their conscience to a group of strangers that then Governing Body doesn't even know how to clearly identify (as individuals).
Respectfully,
AuldSoul