Pure water is not a conductor, but combined with oil and minerals; which is what you get from most plant air systems, can be something that does not actually clean but can pit traces plus leave a conductive film that bridges conductive pathways.
The I have done it for 30 years is not a good reference. I have seen people that used air to "blow off" dirt from their clothes etc end up losing an eye or worse. I have seen machines, panels, etc being blown "out" but instead an object gets blown "in" and destroys something.
Canned air can be appropriate at times and many items can be washed with water, it depends. When water is used you must make sure it is dry, tap water has minerals that do make it conductive. It is better to dry boards etc with a heat gun or hair dryer than pressurized air, have to be careful with a heat gun too.
Here is something to think about. Most plant systems maintain at least 100 PSI, 100 pounds per square inch does not sound like much but convert it to another form...7.2 tons per square foot. That is equivalent to a baby elephant standing on your chest.
One, if not the most, talked about issue here is SAFETY, safety does not begin or end with the design of the machine. It begins and ends with ALL the people involved with a machine.
Whether or not there is water, oil, minerals etc in the air, you have to realize that when you use plant air that YOU HAVE A GUN IN YOUR HAND.
Call it nitpicking if you want too.