Comment # 27 on bug 984778 from Tony Mechelynck

(In reply to Benjamin Zeller from comment #26)
> If the "needs rebooting" flag was set or not depends on the zypper version
> that did the upgrade. If you upgraded from a zypper version not having the
> feature to the one offering it, the flag can not be set.

Ah, I see. I upgraded from whatever version of zypper was present day before
yesterday on Leap 15.0, "zypper --releasever=15.1 dup" acted on more than 9000
packages including itself and the kernel, and IIUC it invoked its updated
version when finishing, which couldn't see the flag because the earlier version
didn't know about it. Thanks for explaining.