Then the non-flying pilot calls positive rate and the flying pilot call gear up
Many times I have observed in simulator training the PM anticipating calling "positive rate" when his altimeter hasn't moved and always the PF then calls "gear up" as a reflex. Monkey see - monkey do, syndrome.
You can see this coming when you see the PM moving his hand towards the gear lever
before calling "positive rate"
Far better the PF calls positive rate first - waits for the PM to confirm - then the PF calls "gear up".