Dang, that stinks and even though I found out for certain that it is correct that it won't work in dogfight mode it is surprising and their reasoning is not all that sound, imo, for not adding it to dogfight multiplayer mode.
On this screen you can modify time before bomb/gun/rockets craters disappear. Default multiplier is set to 1.0 for all of them. Default times are also stated (number next to text boxes). By changing multipliers, you can make craters visible longer time. However this only works in single player mission and coop missions. Setting long crater durations in dog fight missions would cause inconsistency between players, since DF mode allows joining anytime.
If that were the case then you couldn't join with anything moving on the map since those require syncing between the server and the player joining too. Imo someone just didn't feel like adding another timer to keep the bomb craters in sync.
I can't think of anything else at the moment that might mimic what you want but if something comes to mind I will give you another shout out.