Why would a coach decide to change his switching strategy because Orlando started two bigs? Especially if we did too?
Because our bigs matched up perfectly against Orlando's bigs. Most teams start one big man and they constantly attack the mismatch. There was no such mismatch yesterday. If Ime wants to impliment a switch-heavy defensive scheme, the least he can do is replace one of Timelord/Horford with a switchable defender. What's the point in running a switch-heavy defensive scheme with two drop bigs in the starting lineup? Not to mention, Schroder cannot switch screens either. This is madness! Mind you, Ime was a defensive coordinator for crying out loud! To be fair, I didn't watch the game against the Bulls. LilRip posted above that we didn't switch everything in that game. If so, perhaps Ime is gradually coming to his senses. Time will tell.
We have problems on defense, but one thing that isn't happening is that our guards are getting punished on switches by centers.
Agreed. What's happening is the exact opposite: Our Centers are getting punished on switches by guards.
Perimeter defense is all about lateral quickness? Really? How come the quickest players in the league aren't the best perimeter defenders? Why has Marcus Smart been a top perimeter defender for years?
To a large extent, yes. On-ball defense on the perimeter is mostly about lateral quickness. You gotta be able to stay in front of your opponent in order to keep him away from the basket. Quickest way to do that is by moving laterally. Smart ain't a top on-ball defender. What makes him special is his brute strength relative to his height. He's ''just'' 6'3'', but he's built like a tank which allows him to switch on taller opponents. I would argue he's the second most versatile/switchable guard defender in the NBA behind only Ben Simmons. Being physically strong comes at a price cause it hinders his explosiveness. Very few players are both strong and explosive (Giannis, Bam and Simmons come to mind). For instance, prime Avery Bradley was an elite on-ball defender cause he was lightning quick, but he wasn't strong/tall enough to switch on bigger opponents. Smart is nowhere near Bradley's level when it comes to on-ball defense. Personally speaking, I value versatility over on-ball defense. Both are very useful skills though.
Robert Williams is clearly quicker laterally than Al Horford.
Agreed, but this means close to nothing. Horford is 35 years old. He ain't a mobile big man anymore.