two-gun Light Defender was an early version of the three-gun
"Heavy Defender", seen in early screenshots about
a year before the game's release. There was also a
"Light Interceptor," but this eventually became
what we now know as the Scout. The Light Defender, having
little utility, was dropped from the game.
Taiidan Light Defender was, as you can see, substantially
different from the final version of the Heavy Defender.