The funny thing is that you write, that he's not a ballbasher and than admit that he does what ballbashers do: "hitting powerful shots to get his opponent off position/draw a short ball and then unleash his forehand". That's ballbashing: hitting the ball hard and fast, bashing it. The problem was that there were not too much of those powerful shots.del Potro is a player of the Djokovic/Murray generation, he's a baseliner - only relying on power/depth/consistency instead of defense/movement... he was never and will never be a ballbasher. It's about time people stop being surprised when he gets often engaged in long rallies; it's not an anomaly, it's his game and has always been: hitting powerful shots to get his opponent off position/draw a short ball and then unleash his forehand. He never ever beat the top players (bar Nadal) by just blowing them off the court, but by outrallying them, by his ability to hit a lot of powerful deep shots in rallies, relentlessly. There's a difference between dictating points and blasting the ball for winners at the first chance, del Potro definitely did try to dictate rallies as often as possible.
Where did you get those groundstroke stats from? That said, although I doubt Novak was hitting harder, it'd not be that surprising, since he can produce much better shots from defensive positions than del Potro, which obviously influences the average. del Potro pushing the ball is an hilarious concept, with his movement he'd be routined by any top 20 player without his power/depth/weight of shot keeping opponents at bay.
It wasn't just Novak, the match has been hailed as a classic already by many, even MTF has more or less collectively agreed on it and you know how negative MTF usually is.
I already said where did I get that stat from: it was one of the stat popping up at the late stage of the match which said that Nole's avg groungrstrokes were a bit faster than Delpo's (1 mph faster on average). Not much a difference, but very telling considering that Delpo's potential in this department is much greater than Novak's.
And I didn't write about it being a classic or not, but whether it was best Delpo's match with a lot of powerful shots. AO 2012 is also seen as a classic by many, but it doesn't change the fact, that it wasn't the best match of Djokovic nor Nadal and there wasn't much power-hitting there.