mRNA may peak that fast, I don't know. But my J&J didn't do anything for two weeks (I had no spike protein antibodies). I finally got some after 30 days. My opinion is slower is better.
Too many variables.
Some jabs are F'd up in manufacturing (as in Baltimore).
Some jabs are sabotaged along the way.
Some jabs are injected intradermally not intramuscularly.
Some people have different absorption of the mRNA in their cells and different activation.
People have different amounts of spike expression in their cell membranes and different amounts breaking loose and getting into the blood.
Some people have different immune responses to the jab, such that any free spike in their blood is taken out quickly, some don't.
And so on, and so on.