[xsl] XSLT 3.0: Are keys really components that a package should care about?

["Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

 In Section 3.6.3 "Named Components in Packages"
(http://www.w3.org/TR/2014/WD-xslt-30-20141002/#named-components ) of
the XSLT 3.0 2nd Last Call, we read:

"This section discusses the use of named components in packages:
specifically functions, named templates, attribute sets, modes,
accumulators, keys, modes, and global variables and parameters. Some
of the provisions in this section also apply to named modes, but there
are differences noted in 3.6.4 Overriding Template Rules from a Used
Package. The section is largely concerned with details of the rules
that affect references from one component to another by name, whether
the components are in the same package or in different packages. The
rules are designed to meet a number of requirements:"

Besides the mentioning of modes twice in this list (and this also
happens at another place of the document), which I hope resulted from
duplication and not from omission, I am wondering why keys are in this
list of named components at all.

As we discover later in the document, an xsl:key always has private
visibility -- therefore it cannot be exposed to using packages,
because a using-package cannot reference a private component from a
used-package.

Is this an error... or if not, could someone explain, please?

-- 
Cheers,
Dimitre Novatchev