I'm certainly no scout, but that has been my take too. When he swings over the top of that slider, missing by 18", it seems that he's almost always swinging at what he thinks is a fastball. Sure, every guy swings and misses on occasion. But not everybody gets fooled as much as Bruce does. Having his swing stay in the zone longer won't help him put the bat in the right spot.
That said, perhaps his swing issues drove him to start his swing too early, forcing him to commit before he had given himself enough time to read the pitch. Perhaps being quicker to the ball will let hit wait longer and get better reads. I honestly don't know, but I agree that it looks like an issue of recognition and timing more than anything else.