If by "elephant" you mean "Ryu", which I'm going to guess you might be referring to, then no it's not a hard counter. While it's true that Ryu automatically turns to face his opponent, this is after the said lag is finished no? And so far, I haven't heard of de-confirmation or evidence anywhere about Ryu automatically turning around to face the opponent if he's airborne drifting or still in tumble fall. If he can't turn around to face you in the air, and if Focus operates the same way, then Backslash won't be useful compared to Uair destroying the option. Even so, the panic factor can play a role and can still Backslash Ryu if he cannot turn around while airborne.
Otherwise, If it's not Ryu, then who is the unwinnable matchup?