If a plumber is punctual they would arrive on time and one doesn't have to sit all day waiting for them so the speaker is being sarcastic.
Context: "Water is not working in the house and I have been sitting here all day waiting for the plumber to show up."
Hypothesis: I have been sitting here all day waiting for the punctual plumber to show up and fix the water issue in the house, but nobody has arrived yet!
Based on the context, is the hypothesis true, false, or unknown?