Your images imply that the master keys are derived from the entropy used to generate the seed phrase; however, the phrase itself is used as input to the PBKDF2.
they are just out of context here since they are explaining two different BIPs on separate contexes. the first one is explaining how to get the mnemonic from a 128-bit entropy using BIP39 while on a completely separate topic the second picture is explaining how to get a child key from a 128-bit entropy using BIP32.
if it were going from mnemonic to child key, the second picture should have used the 512-bit entropy as its start.
