I mark it as irrelevant as it plays no essential role to what the rest of the game would lay out, and is the only time you will actually utilize the flashlight mechanic.
If this mechanic were expanded upon in the game, then the first level would play an essential role in teaching the player what to do. However, since this is not the case, it becomes almost a red-herring. It teaches the player something that is irrelevant to the rest of the game and no new information that would help in the levels after that. Therefore, I would be inclined to say the first level in it’s current formation is irrelevant from a design standpoint.