rotating text by 180° over two lines partially disables horizontal centering

In Calc, I open a new document, and set row height as 1,20 cm. In cell A1, I write some text over two lines (“X Y Z\nY”). I also format it as horizontal=center and vertical=middle, and all is fine, that is, the “Y” on the 2nd line is below the “Y” on the 1st line. I can’t upload a screenshot as I have <3 points, so here is a sketch:

     |       A       |
     |     X Y Z     |
 1   |       Y       |

However, when I copy this cell into A2, and then rotate the whole cell content by 180°, the second line isn’t properly centered anymore . In fact, the “Y” from the 2nd line (which became the 1st line after rotation) is now below the “X” from the first line (which became the 2nd line after the rotation).

Did I make a mistake? Is this a bug?

ps: my system is xUbuntu 14.04 with LibreOffice Version= BuildID=1:5.2.3~rc2-0ubuntu1~trusty1 OS Version=Linux 3.13, Locale=fr-FR

There are several bugs about the matter Rotated text bugs