First of all, water can introduce bacteria into the ear, which can lead to an ear infection. This is one reason why many knowledgeable people are against the use of spray bottles for disciplinary purposes. So for this "expert" to say that water in the face will not hurt a cat is grossly irresponsible.
Even proponents of the spray bottle recommend aiming at the cat's backside, not at the face. Personally, I find deliberately spraying water at an animal's face to be rather insulting.
Secondly, spray bottles tend to not work particularly well because they aren't necessarily around when you need them, the water stream is not easily controlled so one's aim can't be as accurate as it needs to be for the reasons mentioned above, and inevitably even the dumbest cat will (a) learn to associate you with the unpleasant sensation of being hit with water, thus possibly leading to worse behavioral issues, and (b) know that he/she is safe from punishment as long as you're not around.
Finally, there could very well come a time when your cat needs to be bathed immediately. Is it really a good idea to cause the cat to associate water with punishment or bad things? Most cats already have a disinclination towards water; why exacerbate it?
Expert Village my