Does 12 word Mnemonic seed + passphrase wallet get recovered w/o the passphrase?

I recently bought an Ellipal Titan, I was playing around with it to get used to the wallet.

  1. I created a wallet with 12 mnemonic + passphrase.
  2. I erased the wallet.
  3. I tried to recover the wallet with the same 12 word key + different passphrase.
  4. I was able to recover the original wallet with the different passphrase.

I wonder how this happen. Is it supposed to that way, or Titan is messed up? It seems as though using passphrase does not affect the security at all. Any idea?