Close! They were talking about Stephanie's pack and Lydia!

:D Stiles just lost track of time, what with all the sex, how could anybody expect otherwise? His professors would have understood!

Oh, yeah, you're right -- Derek is treating his own experiences as universal, but he hasn't had all that many experiences, really -- more than enough to make Scott think he knows everything, but he's never even been part of a pack as an adult. So it is perfectly possible, yes.