DOCBOOK-APPS: No Separate Title Page for an Article

Hello!

I'm wondering why I don't get a separate title page for an article in
print output even though I got

(define %generate-article-toc% #t)
(define %generate-article-toc-on-titlepage% #f)
(define %generate-article-titlepage-on-separate-page% #t)

in my customization layer.

I'm using DSSSL style sheets version 1.69.
What's the cause of this problem?

Thanks in advance for any help!

Greetings,

	Holger