That tool generates a random salt, so passphrase cracking time is O(n) where n is the number of files being cracked vs O(1) for Minilock public keys. Additionally, encrypted files are generally still not "public", whereas Minilock public keys likely would be.
Assuming that all files are encrypted with the same passphrase, and you crack the passphrase, not the key generated from kdf(salt, passphrase), complexity is O(1) for Minilock as well.
