There's nothing that I've read that says both pilots can't log P1 during the same leg and I think this is what Pablo may be referring to.
Example: Pilot A takes off, flies to TOC. Hands controls to Pilot B, who flies a 3 hour cruise. Pilot B then takes controls, flies the approach and lands.
Pilot A P1 = 1 hr
Pilot B P1 = 3 hr
Anybody agree?