Now this seemingly harmless item has "broken" the game.
Nah. The game was broken by a lazy, unskilled DM (who is also potentially ignorant with respect to the magnitude of the proposed task, as well as dungeon design) that decided to have lazy, unresponsive, inactive dungeon residents who let a party perform a major construction project (a dam or other containment "pen" large enough to hold water volume similar to the dungeon and something to channel the flow of said water, all quite close to the dungeon entrance), fill said reservoir, and release it, all without molestation.
The game's tactical focus, if any, has little to do with it.
While I am not [MENTION=23094]Patryn of Elvenshae[/MENTION], I can see where his (or her?) argument comes from. I don't honestly believe "anything" can break the game. +1 sword? I can't see how that can break a game. Decanter? Perhaps in a world-building sense (as in: every city in the desert should have one or more, and the presence of one could let a small settlement spring up in a desert pretty much anywhere), but not in an "overcoming challenges" sense (unless acquisition of water was the challenge, but by the time you have 9k to "spend" on a decanter, that's likely a trivial challenge). Heck, most magic items are in the same category.
Contrariwise, there are things that can break a game regardless of the intended vision or lack of such.
[sblock="Aside:"]Well, I suppose the caveat applies that I automatically think of the basic premise -- a team of adventurers that, roughly speaking, work together to do things generally too dangerous for commoners to attempt -- should be held up as an inviolable vision. Note that doesn't imply heroics. The adventurers may be black-hearted mercenaries, or they may be heroes of destiny, or even aspiring tyrants. The important bit is, essentially, "go on adventures" as opposed to "run a village smithy (or similar business)." The "team" bit is pretty important, too, though I have played and DMed solo PCs.[/sblock]Unless you are emulating the Ars Magica meme, a lot of high level magic (and even some mid-level stuff) can "break" the game.
Similarly, presenting two options as "balanced" or "equivalent" when they aren't can break the game if fairness is any small part of your vision for the game. (Example -- though some will disagree with it -- The 3.x fighter is simultaneously handicapped in out-of-combat utility and underperforming in most high-level combats. The wizard or druid, on the other hand, have markedly more out-of-combat utility, in-combat power, and easy flexibility to change focus.)
Anyhow, I agree with you that broader focus of activities can make the game harder to break, but disagree with some of the specifics of both statements given by your quote, below.
Everything can "break the game" when you give the players enough freedom.
[and]
Even more, you can only "break" the game when you have a very specific vision of how the game should be played
