I ride Moultons, they similarly feel wobbly at first. (I also owned a Brompton about ten years ago, but didn't enjoy riding it due to the lack of front suspension, which necessitated watching the road surface very attentively to avoid road defects.)
The true term is more responsive! I have always (so far) been able to catch the bike when the front wheel has slipped sideways on a wet patch, something I have never managed on a large wheeler. Yes, it does mean you can't ride no-hands (at least for most of us), but who wants to anyway?