I didn't say it wouldn't leak if I pressurized the system using the engine driven compressor.
When I start the engine I am usually going to drive away and with the engine running there is not way to hear a leak. However if I shut down for lunch at a rest stop, I don't notice it, but then again is is noisier at a rest stop than it is in my garage. I think exercising things makes them work better so that might be why it is not noticed when the engine is compressing the air.