src/java.base/windows/classes/sun/nio/ch/PipeImpl.java

    /**
     * Creates a (TCP) Pipe implementation that supports buffering.
     */
    PipeImpl(SelectorProvider sp) throws IOException {
        this(sp, true, false);
    }

The first boolean is `preferAfUnix` - the second one is `buffering` - so this actually creates a Unix Domain pipe with no buffering.

Either the spec or the implementation should be fixed so that they both match.

Note that the only place where this constructor is used seems to be here:

src/java.base/share/classes/sun/nio/ch/SelectorProviderImpl.java:        return new PipeImpl(this);