It's a carryover from Striker: the Block value is used as a negative DM for melee attacks made against a person using that weapon to defend with. Where the task description on p.69 refers to "weapon defense" it means Block value.
As for the weapons without Block values, that is (surprise, surprise) errata. The missing values are Sword - 3, Cutlass - 2, Broadsword - 2. NOTE: If you're trying to play MT without incorporating the errata you're making things a lot harder for yourself -- it runs many pages long and is available for download somewhere at downport.com. I very highly recommend tracking it down.