Ah, he’s one of those type-of-coaches. These ex-pros (and recently, too) who are part of, or form their own academy/travel-ball team. Occasionally, they’re control-freaks, and have their players (trying to) do(ing) all these complex things in situations so as to exert “pressure” on the opposing team. They count on having local umpires who either kowtow to their having been a pro, or are old (or “way too young”), and they can “outfox”.
While I like @Velho’s and @Coach Carl’s interpretation and imposing a penalty reflective of the “crime”, I can also see @Richvee’s point. What if the pitch had been a ball? What if the pitch had hit the batter? With runners aboard, what if the pitch had been wild, and allowed the Runners to advance? The offense should, in no way, benefit from this shenanigan. So, with this being amateur baseball (< college), it’s best practice to call No-Pitch, with the penalty of a strike because the batter left the box during the pitch.
Then, just lay into that “coach”.
I’m not going to let him even get that far. Whether I’m on PU or BU, I’m going to verbally chastise him, starting with he can’t just “call Time” (coaches request Time; Umpires grant / call Time), he can’t just walk in the field during Live ball, he can’t interrupt a pitch like that… need I keep going? I’m going to throw it all on him, right up front, and there won’t be any “wriggle room” for him to even argue anything.
The only reason I wouldn’t outright dump him, is in that environment, he might be the only “coach”, and if dumped, his team likely forfeits; I wouldn’t want to affect his players so drastically due to his attempted antics.
It’s bad enough when a coach makes a mistake and leaves his pitcher in longer than (limited) pitch/inning count, and we’ve got to forfeit the game.