The same is true with other things. The automobile driver is never taught to avoid picking his foot up from the throttle abruptly before slowing down or stopping. But what pilot would snap his aircraft engine to the idle-stops as readily as he does his car? (I know...but let's not digress into discussions about liquid-cooled auto engines, and thermal dynamics, etc., OK?)
The point is, that we teach smoothness for more purposes than first meets the mind's eye. Smoothness requires planning ahead of the aircraft. And planning ahead of the aircraft involves an entirely new mind-set from the habits of most car drivers. (Just try sitting silently in the right seat while my favorite brunette drives you around in the Texas "hill country" and you'll quickly see what I mean.)
Anyway,...I'm not advocating yanking the throttle off to descend. I'm only trying to alleviate fears of bringing an engine all the way back to idle in flight. It should be done smoothly, and with some consideration for the gyroscopic and other stresses as well as thermal ones that the engine must go thru.
Re: your question regarding my personal experiences: I've flown these cylinders (they're basically the same in all the "C" engines made by Continental) in C-65/75/85/90 and O-200/O-300 families of engines for about 5,000 hours (3500 of them mostly in 120/140/150 aircraft in flight training and utility operations) and I've never experienced a cracked cylinder. I can't tell you the numbers of times I've abused those O-200's by pulling the throttle all the way off in cruise and saying to my student, "Ok, NOW where would you put this thing down?"
Those airplanes were sent through stalls followed by slam-acceleration recoveries, touch-and-go bounce-drills, and on and on ad nauseum by a half-dozen different instructors and 100's of students and several worn-out engine overhauls but not a single cracked cylinder in the fleet.
I've had 5 cracked cylinders in higher-performance corporate aircraft that were flown only in passenger operations by professional pilots and were never so abused. The director of ops had nightmares of pilots yanking throttles off because of cracked cylinder problems in those IO-520's/TSIO-520's. I never once saw any of those professional pilots perform anything but a 1" MP per-minute-type descents because of the director's paranoia-induced threatening lectures,...but the cracked cylinders just kept on coming. He never understood it had nothing to do with "shock cooling" because the pilots never allowed the engines to be "shock cooled".
But there's simply no way to avoid those 1500-degree EGT's during takeoff and using re-built cylinders with unknown histories sure didn't help matters any. (None of the TCM remans which used only new cylinders had such problems. I can't recall a single cracked cylinder on those engines. Loss of compressions from poor quality control during manufacture,... yes, ...but not cracked cylinders.)
