I accept what you say but it must be because of a fault or poor operating. When I worked abroad I used SSB to communicate with our parent centre. It was instantaneous in both directions and that's going back nearly 40 years using rather poor equipment! Transmitters don't need "powering up", they should operate the instant you press the transmit key.. Maybe Mil Volmet uses VOX, which is a system where the transmitter operates the instant a noise is heard in the mic. VOX has a delay function so if that is wrongly set up it could produce the effect you are hearing..