Available with LIB version 2016.3.1205, it will be also available in the 2017 R1 release.
As advised in the forum thread, the behavior is expected. Please refer to the thread for more information.
In UI for WPF R1 2017 (2017.1.117),
the problem has been fixed only partially:
Thank you for the quick processing of my request and the quick bug fix of the issue.
I am looking forward to the next release of UI for WPF.