Beta 5 .83 Doing battle in Radiation Storm removes 25% hit points even if no damage taken

Not sure if this is a bug or WAD.  I had thought that the -25% hit points penalty in a radiation storm nebula meant that while you were in the nebula, your hit points were temporarily reduced 25%.  For example, a ship with base 60 hp would be treated in a battle as if it had 45 hp, and then after it emerged from the battle and nebula, it would have 60 hp again.  How it works, though, is that if you have a battle in the nebula, you lose that 25% hp even if your ship took no damage in the battle.  So you go in with 60, suffer no damage, and come out with 45 needing to repair 15 hp to get back to full strength.  Is that intended?