1) it means that attack actions are special cookies that interact with blocks in very nonstandard ways - which is unfortunate, given that all of the obvious examples of blocks in the book are based off of attacks.
I think this is a bit of a simplification that is actually sort of inverted. Think about it this way.
An attack is a contest (an opposed action) where the margin of success is important. Blocks reduce their effectiveness.
A maneuver is also a contest, however the margin of success is less important. The only time when blocks reduce their effectiveness is when the block strength and the shift value of the maneuver are both dead even. A rare event, but technically still an instance of the block reducing the effectiveness of a maneuver.
A block is a simple action (in other words an unopposed roll) with no difficulty. Even a grapple is unopposed despite being directly conflicting. Having no difficulty means that there are no margins of success or failure. A block does not reduce it's effectiveness, because the block has no margin of success, it succeeds or does not.
So to be technical it is actually the block that interacts differently with a block. The attack works the same way as any other contest.
Personally though I think I would apply the block strength as a penalty to the margin of success in some things but not others (attack, maneuver, move, spell control but not blocks, or non-conflict actions). I'm thinking it would primarily have to do with whether the margin of success was important, not whether the action is opposed. But that's because it's the game I want to play, not cause the rule book says so.