Just used common sense what it shown in manhwa, what it means by the title that fandore harpe got, his real name is "giant hartail fandore harpe", there is a chance that traum can minimized it because it got name "giant" and no mention about "small hartail fandore harpe" if it different, and the title "one of seven animals that directly controls out of 23 beasts" it can be means no BHs own or control it only traum own it and control it, and no one mention something special about "giant hartail fandore harpe" when it appear.
The title same with his octopus, but the special about his octopus is as lefav mention "it has strong own will only few could control it in the past and she said she think it impossible to command octopus that big" so as traum can control that big special octopus, he didn't used it as fandore harpe used.
*add another traum summons
Sea dragon, that yama didn't know what is that, no one comment about it, that can be means sea dragon is so rare plus levi too when it first appear no one in there know what creature is levi maybe only 10 FH knows about sea dragon.