Paul Winalski wrote:
I found out that the difference between rapid-rise yeast and regular yeast is that rapid-rise is compounded into smaller granules than regular yeast, so you can add it directly to the dough and skip the proofing step. But that runs the risk of using yeast that's dead.
-Paul W.
Instant yeast granules are quite porous, too, manufactured with a very high ratio of surface area to volume. Sorta like activated charcoal.