It is not the check or the select. It is the way the substitution has been implemented. It looks like the code replaces the variable name and not the value. Which is different from what is written at page 800. I only hope they won't change the manual to match the feature/bug (warning: new joke)
Page 800:
"Another restriction on parameter symbols is that they only work in SELECT, INSERT, UPDATE, and DELETE commands. In other statement types (generically called utility statements), you must insert values textually even if they are just data values."
