Judging by his clothing, wherever he was from, he must have been important. He held the stature and physical appearance of someone with great wealth and power. But on the TARDIS? He was the same as anyone else. And to Gabriel, he was just another human.
"No, I don't know who you are" he replied with a mild Southern drawl. "Baron Wulfenbach then, I assume... You can call me Gabriel" he added. Malkuth was a name reserved for his Angelic form. When he wanted to play human, he was Gabriel. "You're on the TARDIS. Like I said, it's a ship. And we're all stuck here" he explained. "I have no idea how long we're going to be here but you should probably make yourself comfortable" he suggested.