While walking along a beach (I checked it was an actual beach "biome" by pressing F3) I suddenly realized there were no palm trees generated at all in the new chunks.
Even weirder : when going in the same seed in Creative, at roughly the same coordinates, I had the same issue and I couldn't even find palm tree saplings in the creative menu, despite all the other saplings being present !
As far as I know, this bug can be reproduced by making chunks contaning beach biome blocks generate, on any world.