The Xenial desktop images run the installer with title bar that says "Install (as superuser)". The "(as superuser)" part feels like a forgotten debugging string.
I've seen this on both the i386 and amd64 images.
$ sha256sum ~/Canonical/iso/ubuntu-16.04-desktop-*
4bcec83ef856c50c6866f3b0f3942e011104b5ecc6d955d1e7061faff86070d4 /home/sarnold/Canonical/iso/ubuntu-16.04-desktop-amd64.iso
b20b956b5f65dff3650b3ef4e758a78a2a87152101a04ea1804f993d8e551ceb /home/sarnold/Canonical/iso/ubuntu-16.04-desktop-i386.iso
Thanks
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Tue May 17 17:27:50 2016
InstallationDate: Installed on 2012-10-18 (1307 days ago)
InstallationMedia: Ubuntu 12.04.1 LTS "Precise Pangolin" - Release amd64 (20120823.1)
SourcePackage: ubiquity
UpgradeStatus: Upgraded to xenial on 2016-04-30 (17 days ago)
Thank you for taking the time to report this bug and helping to make Ubuntu better. We noticed that you were installing the LTS version of Ubuntu using an older version of the installation media. The latest point release of 12.04 is 12.04.5. Please try installing from that version of the installation media and see if that resolves your issue. Thanks in advance!
[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]