I think he was possibly being sarcastic. I rehydrate always now. It's easier to pour into a carboy and it's better for yeast health. Do whatch you want.
There is absolutely no reason to rehydrate, other than the fact that the rehydration process (in water) allows the dry yeast to re-build cell walls and to absorb the nutrient built into the drying process prior to the metabolic stress of the wort sugars being introduced intracellularly. The viability is nearly doubled by rehydrating with water.
To me that actually sounds like a pretty good reason to rehydrate.
I've done it both ways and never noticed a difference in performance. However, I've never performed the infamous blind triangle tasting either.
Not really sarcastic, because I think it works either way, so I agree with those who choose not to do so, but I prefer to do so, for the reason stated - cell wall stabilization and proven greater viability. When I said "reuse of dry yeast is trickier" I just meant that it is trickier than simply repitching the entire yeast cake - i.e., trickier than the initial question of whether to rehydrate or not.