com.thoughtworks.xstream.core.util is not exported in OSGI manifest

com.thoughtworks.xstream.io.xml.PrettyPrintWriter uses com.thoughtworks.xstream.core.util.QuickWriter in the method:

PrettyPrintWriter#writeText but this type is not exported in the OSGi Manifest so one can't use this type in client code.

I'm using the latest release from here:
https://mvnrepository.com/artifact/com.thoughtworks.xstream/xstream

it seems it is explicitly removed from export here:

xstream/xstream/pom.xml

Line 423 in d03f698

    
           <bundle.export.package>!com.thoughtworks.xstream.core.util,com.thoughtworks.xstream.*;-noimport:=true</bundle.export.package>

but I wonder what is the purpose of that?

Instead of experting the package, it mit be possible to have some abstraction or move QuickWriter to the com.thoughtworks.xstream.io.xml package...

Yes, that package is for private use and does not provide any API stability. So, what's your use case for QuickWriter apart from the fact that it is in a protected method?

If it is private I think it should only be used in private methods as otherwise it can drip into user-code anyways.
I'm currently using it to add a CDATA section into the emitted XML code like this:

CompactWriter compactWriter = new CompactWriter(writer) {
    boolean cdata = false;

    @Override
    public void startNode(String name, @SuppressWarnings("rawtypes") Class clazz) {
        super.startNode(name, clazz);
        cdata = name.equals("sectionText");
    }

    @Override
    protected void writeText(QuickWriter writer, String text) {
        if (cdata) {
            writer.write("<![CDATA[");
            writer.write(text);
            writer.write("]]>");
        } else {
            super.writeText(writer, text);
        }
    }
};