The rule specifies two conditions for a legal spike to stop the clock: it must come after a direct, hand-to-hand snap (no shotgun), and it must be immediate. 7-5-2e EXCEPTION
The first is pretty straightforward. The second is a judgment call: but clearly the QB needs to take a step or two back from the snapper in order to have space to spike it.
The purpose of the "immediate" restriction is to prevent a team from running a play, failing to find an open receiver, and then deliberately grounding the ball in order to conserve time.
Perhaps the coach was confabulating, or confusing something an official told him, or even reporting correctly something an overzealous official did in his game. Who knows? All you can do is understand better what the correct answer is!
