Bcrypt double 80110ck5

[Barkin]

If the pass phrase used to encrypt a file with Bcrypt is the same series of characters repeated, e.g. 80110ck580110ck5 ,
that Bcrypted file can be decrypted with without the repetition, i.e. 80110ck5 will unlock the file.

Why isn’t 80110ck580110ck5 required to decrypt the file ?

[the passphrases are not being truncated at eight characters, I've checked]