I think it could be helpful, but... I'm wondering the "density" difference of water with a Specific Gravity of "1", and air = assume a "0".. you may discover a "leak" that you wouldn't find when wet. I have no factual information at my fingertips, except that when we are testing a water pipe, it must be done wet. If the calculated average volume is expected to be 1/4 to 1/2 full then we must fill the pipe to at least 2/3 full and then cap and tap - add air to what ever spec is required. If you use Nitrogen, the molecules are larger than Oxygen molecules and again will show no leaks but then when you charge with air.. you'll have a leak. This is why the tire shops offer a filling with Nitrogen for a couple bucks as you (theoretically) won't lose tire pressure when filled with Nitrogen.

My thoughts fwiw... LOL.