Now we're talking sense. Most people will drop their heel to varying amounts under load, I certainly do. So I set my saddle so I can lock out my ankle when I drop my heel and have a roughly straight leg at the same time. While riding I don't normally lock out my ankle, so this ensures I always have a bend in my knee under load. Many set their seat much higher and pedal toe down, fine if u like that but often it is combined with a huge stack of spacers under the stem and a rider with a bad back. They still ride with a bend in their leg but they can't drop their heel. In other words the bike restricts their movement.

One bike fit I had set my seat so there was a 40 mm gap from heel to pedal, how am I supposed to drop my heel in that position! Extremely uncomfortable but the fitter said it would make me more powerful - epic fail