Also Würstchen hin, Senf her, laut Doku ist es so:

Regarding the installation of SLIC, i5OS base software and licensed programs,
the following limitations apply:
 Installing SLIC or base operating system using Virtual Tape is currently not
supported.
An IPL from Virtual Tape is not supported.
Even if IPL from an optical image catalog is supported, an IPL from a tape
catalog is not possible today.
Scratch install from a virtual tape volume is not possible, since there are no
virtual tape volumes on the system at that time to IPL from.
In case you have to install a system from scratch, you can either use a
physical optical drive or physical tape device as alternate IPL device.
 Restore of licensed programs (RSTLICPGM) is supported.