Would be great if it was true... at least on macOS the routine cannot be found in the help unless the unit name already appears in the Uses clause.
Given the book was published at the end of 2012, is this a regression in the IDE?
No idea if it used to work...
But for finding the unit => install package cody.
Cody adds "Menu: Source > Show Unit/Identifier Dictionary".
As you work with codetools, this dictionary will be created, so if it is empty, just continue using the IDE.
Then you can use it to find any identifier. And it will add the unit to the uses when you select it.