The HP-UX /etc/securetty must be group-owned by root, sys, or bin.
Root, sys, and bin are the most privileged group accounts, by default, for most UNIX systems. If a file as sensitive as /etc/securetty is not group-owned by a privileged group, it could lead to system compromise.
How this relates to the STIG checklist: STIG vs SCAP benchmark.