The whole passive/aggressive scout roles is a relatively new idea and I think it's very unnecessary, even damaging, to define scout roles like that. With soldiers it's necessary to define roles because one is usually running gunboats which making them better suited for bombs and distractions and unsuited for protecting the medic. On the other side of the coin the scout duo usually run the same gear which allows them the freedom to adapt roles with ease. TF2 is a very fast-paced, dynamic game and you need to be dynamic to succeed. The best scouts are the ones who can read their environment and play off their teammates instead of restricting themselves to one particular playstyle.
For example: let's say your scouts have defined scout roles and the "passive" scout is on enemy crates and the "aggressive" scout is on the point at badlands mid. Your team knows there's a half-health soldier in their yard. If the scouts follow their roles instead of playing off of other and being dynamic then the passive scout will go back and cap and the aggressive scout chases down the soldier in yard. Since it would take longer for the "aggressive" scout to reach the soldier the window of opportunity to frag may have closed. A much more efficient approach would be to have the scout closest to the soldier chase him down instead of having the scout who is far away do it.
This is what it is okay; I said empty your mind. Be formless, shapeless. Like water. Now you put water into a cup it becomes the cup. You put water into a bottle it becomes the bottle. You put in a teapot it becomes the teapot. Now water can flow or it can crash. Be water, my friend.