Afaik. For the paperwallet, the entropy is only 18 words (192+6 bit az checksum), and the other 9 is for constructing the wallet or spending password (I cannot recall which one) and the max entropy can just be 256bits for the master seed, due to the blake2b_256 hash. I created some picture for the 12-word mnemonic in the past, see attached.
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