>>> "Alan" == Alan Mackenzie <acm@muc.de> writes:

   > Hello, Uwe.
   > On Wed, Nov 14, 2018 at 13:07:37 +0100, Uwe Brauer wrote:
   >> >>> "Eli" == Eli Zaretskii <eliz@gnu.org> writes:


   >> > I don't know, because it works for me.  Did you try in "emacs -Q"?


   >> I also  tried out emacs -q and it works as expected, but when I start
   >> emacs 

   > Please don't confuse "emacs -Q" with "emacs -q" - they're not the same.


I know. Sorry for any misleading comments.


   > Hope that helps!

The point is, as I wrote in a later message:
it is the version of emacs which makes the difference

So 

emacs25 -q (or -Q) 

shows the behavior Eli was mentioning and which I
was expecting

However 
emacs27 -q (or -Q)

Shows the new behavior 

(Z in dired mode does not uncompress tgz to tar, but extract it
contents!)