That goes down as a dropped pass, but that is not a good throw. Stretching a WR with a high pass like that and exposing him to become a rib sandwich is about the equivalent of LT whiffing and allowing a free shot on the QB.
At first blush it looks too high. But look at the DL, can't catch the number but it begins with a 7, who comes in from RDT or RDE but shifts left and gets his arm up. Tannehill either guns it just by that guy before he gets into the passing lane, or just over his outstretched hand. Kinda tough to tell. So, while it's a tough catch for Rishard Matthews, it may be the only throwing lane Tannehill has. Coaches tape will reveal a better view, but from this broadcast tape, it sure looks like Tannehill trusting his WR to make a play, and firing a bullet high but where his WR could get both hands on it. I'm OK with trying this play, even if it is incomplete.
To me, this looks like Tannehill using his peripheral vision for the entire field, holding the ball until a window opens up, and gunning it before the window closes ... or throwing it over the DL but with enough velocity to get to the WR before those DB's converge on him. Tannehill throws it earlier, Matthews hasn't reached the window, later or softer, the window closes on Matthews. If Tannehill throws a beautifully catchable ball, it likely gets batted down by the DL. His other options would be the check down, scramble to reset the play, or run. Personally, I like the desire to try to gun it in there for an explosive play. This is what pre-season is all about. He has already shown his ability to dink and dunk. Matthews has already shown his ability to be physical and catch a TD in traffic. These type of explosive plays don't happen without practice while the bullets are flying ... so hey, why not give it a shot in a preseason game?
