There's another wrinkle to this, though. Intentional grounding usually requires there not be a receiver in the area. When the ball is snapped, the tight end is clearly in the area, so an eligible receiver is in the area. If it's not a spike, it's an incomplete pass, which would also stop the clock. It's not unlike throwing the ball in the dirt on those failed screens we do all the time.
It's not a delayed spike. It's not spiking a stopped clock (because the clock moves when you snap the ball). It might be a legitimate incomplete pass. There's nothing explicit in the rule book that defines this as intentional grounding that I've seen thus far.