As Rory said, our discussion around this was going on during the same time frame as the site design and graduation. The results of those discussions have been largely captured in the FAQ, now found here:
IT Security Stack Exchange is for Information Security professionals to discuss protecting assets from threats and vulnerabilities. Topics include, but are not limited to:
web app hardening
social engineering, including phishing
physically securing the office, datacentre, information assets etc.
The last two topics are really the core of what you're asking. Incident Response being a largely soft topic, with technical aspects depending on the incident. Then the last is explicitly allowing physical security topics. We do have a number of them already, not nearly as many as some other topics, but as of right now we have 100 non-deleted questions in the physical tag.
The reason for the "IT Security" branding is exactly what Rory hinted at. By the time we had the discussion explicitly allowing physical security questions the site design had already gone through and either had gone live or was within a day or two of going live. We decided it probably wasn't worthwhile to lobby Jin for a new design removing the dreaded "T".