That's a bit of an overstatement; it's responsible for very few technical decisions in Debian, and doesn't normally have even a theoretical ultimate-decision-maker role of regularly reviewing or steering them. Their only role is technical dispute-resolution, and they are supposed to wade into even that as minimally as possible. Most technical decisions are made by a mixture of individual package maintainers, the Debian Project Leader and release-management team, and informal consensus-building. To the extent there's an "ultimate" technical decision-maker, I would say for the majority of issues, the release team working with the project leader functions in that role.

What does that really mean? Debian is a community project, not a hierarchical organisation with a managerial chain of command.

The Technical Committee seems much more like an advisory board and the forum for and arbiter of the tiny number of contentious issues.

They're not involved in, informed of or responsible for the vast majority of technical decisions.