Debug bcrypt iterations with a static salt

I want to debug bcrypt rounds with a static salt using this python lib

import bcrypt
salt = bcrypt.gensalt(14)
password = b"foo"
foo_1_round = bcrypt.kdf(password, salt, desired_key_bytes=10, rounds=1)
foo_2_rounds_manually = bcrypt.kdf(foo_1_round, salt, desired_key_bytes=10, rounds=1)

foo_2_rounds = bcrypt.kdf(password, salt, desired_key_bytes=10, rounds=2)

I expected to see equal foo_2_rounds and foo_2_rounds_manually