An excellent point that illustrates what I was trying to say
Although I doubt any macro-civilization would go to so much trouble just to produce bipedal tetrapod humanoids...
However, I can think of other future sentient designs and body plans they might favor for reasons of their own. They might want to program for certain biochemical, cultural and behavioral characteristics, too.
At any rate, I'm glad to see some writer in that franchise went to the trouble of trying to explain why all the aliens looked like dudes in rubber suits.