No doubt on the bottoming out issue, it would just be interesting to definitively confirm that the bump stop itself is the root cause of the failure by trapping the grime and moisture. I've extensively discussed the exposed rod issue in an earlier post somewhere...general consensus in the off-road world is exposed shafts allow the dirt and grime to be flushed away as opposed to trapping it where it can be forced in to the seal causing pressure failure.
I see the arguments for the exposed shafts, but it may be beneficial in limited scenarios. For a slow offroader (like a modded Wrangler for rock-crawling) then it makes sense. The wheel articulation will cause the shock shaft to get cleaned by movement in addition to open exposure to water for cleaning. Another factor is that debris isn't likely to hit the shaft directly during high speed driving for those kinds of vehicles as they aren't commonly running at very high speeds, let alone driven daily.
However, for vehicles that run regularly at higher speeds for long distances like a sedan, I can imagine that debris kicked up by the tires may damage the shaft over time if it's fully exposed. Dirt and road debris getting kicked up at freeway speeds may pit the shaft over time and cause sealing issues in the shock. Also consider that sedan shocks are much smaller and less robust than larger, beefier offroad truck shocks.
While Suzuki's revised bumper stopper design may not be a silver bullet fix for all Kizashis everywhere, it does seem to reduce premature shock failure for some. It certainly did for me. My rear shocks gave out about a year after I bought the car. If I recall correctly, it didn't even have 20,000 miles on it then. Since the replacement with new shocks and the revised bump stoppers, my Kizashi's rear shocks have held up just fine even to this day with 75,000 miles on the odometer. 70,000 of those miles were out in the East Coast too.