Chlorine gas and germy water reserviors

[SpreadsheetGamr]

So about that chlorine gas killing waterborne germs inside a reservoir...

IMO it goes way past exploit and is by far the silliest thing in the game.  It's counter-intuitive and yet very easy to implement, which is horrible design - bad for new players as they're unlikely to devise it on their own.  Worse, it bypasses a much more technically challenging solution to the problem.  It's like you put all these puzzle pieces in the game and then say just ignore all that and use this one neat trick.

Please, please, please tell me this is not intentional or working as designed?