I'll give the same speech here as I do in noobie mixes.
The idea of passive and aggressive scout *does* exist to a degree in the game, but the problem is with the words, at the risk of sounding like a Wittgenstein fan boy, its the fact that the words passive and aggressive mean different things to different people, hence the danger in their use. Passive scout to any number of scout players may have numerous different connotations as to what that sort of behavior would actually be.
Instead here are some different terms I have invented with the intention for them to apply mostly to mid and stack pushes (although scouts are interchangeable post-mid).
Passive Momma' Bear scout. He protects the demo at mid, but he doesn't avoid damage - he spams a few chip shots, and watches his cute little cubby (the demoman) do his spam thing. But, as soon as somebody attempts to harm the demo in any way shape or form, the momma bear scout transforms from a gentle giant who likes fruits and nuts, into a godless, soulless, killing machine - who then tears out the throat of the nearest opposing player. The momma bear will also tend to be the scout that gets pulled into the combo on pushes, and has to basher build (just for consistency and because they're already acclimated to playing near the combo). But post mid-fight that's not as important.
Then you have, at mid, the aggressive social services scout. If it's found that the opposition has a dead-beat momma bear scout that isn't guarding her wittle cubby, he will take possession of the opposing teams demoman, by turning him into a nice sandwich. If it turns out that they do have an active momma bear, then the social services scout will simply interview their momma bear for a time (ALL A CLEVER DISTRACTION FOR YOUR ROAMER to have some space) and then return to your medic to rejoin your model family near your medic for heals.
Post pushing scout roles are virtually interchangeable and are really a matter of convenience and personal taste/habit or catered to skill sets.