We don't lowball for the sake of lowball
Generally if we know that object A belongs to some Group X, we assume that it has average characteristics of objects in this Group.
Exhibit 1: We know nothing about Character A except him being adult male. We would use average adult male height in calcs involving him, not minimum possible healthy height for adult male.
Exhibit 2: We know nothing about material C, other than it being some kind of steel. We use average values of strength for steel, not minimum values possible for steel materials
Exhibit 3: Lightning range in speed considerably. We use average
speed for it, not the minimum speed.