It was confirmed by one of the FD devs a while back, I'll try and dig out the quote. Otherwise it would be much simpler for players to join the other side and lose (by, for example, launching fighters and getting them quickly destroyed), rather than to bother trying to win for their side.
I'm doubtful that even several CMDRs all launching fighters as quickly as possible could deliberately lose a CZ significantly faster than they could win one and the the influence notifications I've seen showed a lower influence loss for failure than influence gain for success.
Anyway, if that's how it does work, the notifications given by the game must be in error.
It does seem extremely exploitable if you could just join and force a loss easily.
I don't think this is practical.
The cycle time of a dual fighter hangar is generally longer than the TTK of NPC ships and I'm not certain SLFs are worth as much as larger kills (I was under the impression it was related to combat bond value, but I haven't paid close enough attention to the progress bar to be sure). Even if the per-kill progress values all the same, spending fifteen minutes to shoot down all of one's own SLFs then turning on ones own side would make it barely faster to cycle losses than wins and as I mentioned above, the stated influence decrease for losing a CZ is lower than the influence gain for winning one.