Aretha and Nathan are playing in a Modern GPT. Aretha is playing Storm, while Nathan is playing Turbo-Fog. Time is called while the players are in Game 3, on Nathan's turn. Nathan controls multiple cards with Howling Mine-like effects.

After time is called, Aretha says, "I know you have cards like Safe Passage and Silence that will stop my combo. To save time, if you have them, just play them on my upkeep so that I can quickly pass the turn back to you and I won't spend ten minutes going off, holding up the tournament only for you to stop me before I cast my win condition, or in response to it." Nathan agrees and on each of Aretha's three remaining upkeep steps, casts such a card while similarly taking very little time on his turns. The match thus finishes rapidly and is reported as a 1-1-1 draw. (Aretha is not playing any cards like Dispel, though Nathan does not know this.)

Has either player committed an infraction?

Neither player has committed an infraction. Nor would an infraction be committed if Nathan agreed, and then proceeded to cast such a spell in response to the win condition(s).

These “shortcuts” that involve hidden information and more importantly, future game actions are impossible to guide or enforce, and are more like friendly agreements that both players want to actually play the match without wasting their - and the tournament's - time.

Searching for an infraction where there is none will often just lead to your own time being wasted - take a leaf from the players and don't search :D

Infraction? How about giving them a medal, instead?! :)

d:^D

Don't know which “Storm” variant, but if it's the classic “Pyromancer Storm” combo, then it can't be done so easily.

In order to combo off and deal enough damage out of a Grapeshot, you'll have to cast a pretty damn high amount of spells, that go to graveyard and/or exile, when Past in Flames is applied.

The game state is not the same, and in fact, Aretha wins quite a lot of advantage by doing this and not wasting her hand on dozens of spells that will be neutered by a single Fog or whatever.

She might ask her opponent about all that “show me a Fog and I'll pass back the turn for you”, but, were I her opponent, won't accept that “shortcut”, because it's a disadvantage for me.

Cheers!!

Joaquín