That optimum direction is directly facing the sun.
Anything off of dead-center facing the sun reduces the amount of energy that panel can absorb. Admittedly, the amount of reduction doesn't become significant until the sun is maybe 30?? off-center, but that means that during the day, even if you set up in the middle of the desert and point your panels due south, you will have almost zero power absorbed until maybe 10 or 11am local and again by 4 or 5 pm local The farther north you travel, the more extreme the swing of the sun appears and the less sun you get to use.
The idea that this boy has and which you even deduce correctly is that the different cells will peak at different times of the day, but they will all peak and the effective output is relatively stable throughout the day. Yes, I do agree that the maximum output would be lower, but think of it like using a series of D-cell batteries powering a flashlight compared to a capacitor. The capacitor charges up to maximum power fairly quickly and fades away almost as quickly while the D-cell batteries, individually of limited life, could keep the light burning for days.
Now, the problem with your last statement is false to the greater part because almost no solar farms move their panels to follow the sun. I'll grant a few do, and those are the most efficient of the bunch. But you're not going to see that on a rooftop array very often.
