Incorrect stalk thickness for the top of naturally generated bamboo

the top three blocks of naturally generated bamboo stalk are using the wrong size, no matter how tall the plant is. It fixes itself if you add another bamboo manually or if it grows naturally.

Observed:
naturally generated bamboo will have the incorrect stock size on the last three blocks

expected:
the bamboo stock should have a uniform thickness

note: this doesn't happen with all naturally generated stalk, only the ones that are naturally generated with all three top pieces.