So, looks like Yahtzee didn't quite realise that the plot was basically a parody of Modern Warfare 2, and intentionally stole and liberally borrowed the same tropes from across the industry, pausing only to add the explodable buildings. The Battlefield series has never ever pretended to have a decent plot, unlike MW2, and so, because of this and the lame AI, it's a game completely unsuitable for Yahtzee to review.
As for the mortar bit, you needed to stand where the black guy was standing behind cover. I tried to run through it twice before I listened to him shout "get to cover and wait for a break in the barrage" and instantly knew what to do.
The one real area I feel Yahtzee was right was with the really rubbish AI. They know precisely where you are, have ridiculously accurate shotguns but are also incredibly dumb, since they're of the "stand in the open and shoot" variety. Then again, doesn't this just add to the conclusion that the SP is just a bit of silly fun?