Imagine you are at Boeing field, and Boeing is rolling out a new aircraft for its first flight. This specific design has never flown before, but they're pretty good at this whole airplane thing, they understand what goes into it, and everyone with any knowledge understands that this is not a real cause for concern, it just has to fly at some point. All the actual design work, derisking, work with new materials and techniques etc. has happened years ago, and even though technically speaking we haven't seen it work, we all know it does. Meanwhile the empty skeptics are sitting there wondering if the engines will turn on, because "technically" we don't know if they'll turn on this time because we haven't seen it yet.