I came here looking for the same bug. To reproduce, try loading the Caves and Cliffs Data pack that came with original 1.17. I loaded our world fresh with that data pack not long after 1.17's release and hadn't found a single bee nest. I planted at least 300-400 birch trees with flowers nearby and nothing. I just unloaded that data pack and planted a row of six trees and two of them had bee nests.
Justin Barnes
I came here looking for the same bug. To reproduce, try loading the Caves and Cliffs Data pack that came with original 1.17. I loaded our world fresh with that data pack not long after 1.17's release and hadn't found a single bee nest. I planted at least 300-400 birch trees with flowers nearby and nothing. I just unloaded that data pack and planted a row of six trees and two of them had bee nests.