[maaaats]

> My biggest surprise was that the "booster" effect of coffee in the early morning might have been a pure placebo effect

It's not necessarily placebo, but the fact that your body has adjusted to caffeine, so you need it in the morning to reach "normal" levels.

[jacalata]

But he is saying that he experiences the same ramp-up in the mornings without caffeine, so what he thought was the experience of going from uncaffeinated to normal appears to have been unrelated to the caffeine and was actually the experience of going from just-woken-up to awake.