Comment # 6 on bug 915652 from Ancor Gonzalez Sosa

After some research now I know what happened and it's the expected behavior (in
any case, not a bug in YaST).

TLDR; You selected XFCE and the corresponding software pattern does not include
PulseAudio.

And now I'll elaborate a little bit.

During the installation process, an initial system is copied to your machine
and then this system is customized to fit your configuration. That
customization includes removing any package that is on the initial system but
not in your software selection.

You selected XFCE desktop and looks like that software selection does not
include PulseAudio, so the installer proceeded to remove it.

KDE and Gnome patterns both include PulseAudio in any way, that's why the
behavior you described is not experience by most people installing the distro.