Kwallet does not support GPG encryption

[Fabian]

Kubuntu 15.04 (also tried 15.10 beta 2 live)
kwalletmanager 4:15.04.1-0ubuntu1~ubuntu15.04~ppa1
libkf5wallet5 5.12.0-0ubuntu1~ubuntu15.04~ppa1

Despite the delivered documentation, which is also available here https://docs.kde.org/stable5/en/kdeutils/kwallet5/introduction.html#kwallet-create, ubuntu's kwallet does not provide the decision between GPG and blowfish encryption when creating new wallets. Only blowfish wallets are supported.
I couldn't find any documented reason for this. If there is one, the manual (shown when pressing F1) should not contain explanations about the GPG encryption.