I’m talking about the rocks you hop on top of in the cave after you cross the bridge next to the waterfall. To my knowledge, this is the only time these stones appear in a cave, so can you encounter Pokémon on them?
Moving across the hopping stones makes you encounter no Pokemon. I tried using Sweet Scent on top of all the rocks and around 30 times in total as well and the answer is you cannot encounter Pokemon on top of the hopping stones. To verify that it's not just a matter of sweet scent, the second I got off the hopping rocks and used sweet scent in the cave, wild Pokemon and hordes appeared.
Hope I helped! :)