Yeah, no, this is common among shift workers. Typically a tour is a batch of shifts, like if you rotate 1st, 2nd, 3rd, each week of a different shift is a tour, or sometimes the full rotation through all three shifts is a tour and then it repeats. It's not strictly defined and people use it in different ways. Though I'm sure the coppers do love the idea of larping as soldiers and pretending they go on deployment.