I honestly think it'd be handy to have at least one kind of block that a wind charge can reflect off of, so you can build a tunnel for it to continue down. Would make it easier to build an upwards signal transmission.
As a fix, I suggest adding a check for bed spawning to see if there is a portal within the block at and through 2 block above the player's spawnpoint - and invalidating it if there is one. I don't see how that would be difficult to do, either
Confirmed. My assumption is the game prioritizes Bamboo over Azalea and the bamboo is seen as a 'solid' surface for generation.
Update; I just figured out that the reason was I had mob spawning disabled.