While a tankless unit could also leak, it would happen in a different manner and less often.
I have had two tankless leak on me.
An 8 year old unit: Corrosion caused the heat exchanger to leak. Started slow (like a tank heater) and then slowly got worst. We limped along with a leak for over a month until we replaced! The heater was in the attic over a porte cochère so we were note in any danager of s structural damage.
An week old unit: The quick connects inside the unit leaked. It was a manufacturing defect. All it needed was some silicone grease and reassembly.