blowfish ecb with openssl doesn't give the expected result
The -bf-ecb cipher is expanding the key to 128 bits by zero extending it.

The output from -p is the telltale here:

$ openssl enc -bf-ecb -e -in plaintext.txt -out ciphertext.txt -nosalt -K FFFFFFFFFFFFFFFF -p
key=FFFFFFFFFFFFFFFF0000000000000000


Blowfish is defined for 32-448 bit keys, and it appears the OpenSSL implementation chose 128 bits as the size to use, and added zero-extension of shorter keys as a 'convenience'.

Compare this with -des-ecb, where DES is only defined for 64 bit keys:

$ openssl enc -des-ecb -e -in plaintext.txt -out ciphertext-des.txt -nosalt -K FFFFFFFFFFFFFFFF -p
key=FFFFFFFFFFFFFFFF