That's a ludicrous supposition. Anything can be abused. Indeed, we wouldn't have exploits if mechanisms couldn't be leveraged contrary to their intent.
If blocking is to always work, then it has an instancing weight enough to do things like fracture wings, which can absolutely be abused. Off the top of my head, I can think of several scenarios where an infinite-weight block could be weaponized against other players.
Ever wing up with anyone for a RES, CZ, wing mission, or just about anything else? Well, If someone doesn't like a member of your wing, or just wants to be a jerk, they can block one of you and go where you are or seem to be going...then you can waste all sorts of time trying to figure out why you can't instance together, with the trolls never having to expose themselves. Either you start blocking people at random, which runs the risk of significant collateral damage to instancing (breaking the wings of other innocent folk), sod off to PG with your wing, or your wing doesn't quite work as a wing. Hell, if you aren't careful about who you wing up with, such a troll could even be part of it, sabotaging instancing from the inside.