A lid changes heat loss and moisture retention. Comparing an uncovered pan with a covered one is not a like-for-like test of zone performance.
What the observation means
Water quantity, starting temperature and pan base also affect the time. A household observation cannot isolate hob output unless those conditions are understood.
A useful next step
Use the cooking method appropriate for the food and remain attentive. Record meaningful changes under familiar conditions rather than timing unrelated pans. Do not run repeated boiling tests or use maximum power on unsuitable cookware to prove that a zone is weak.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.