Solved
UNC Listening Post Alpha XP Bug
While playing Mass Effect 1 in Mass Effect Legendary Edition, I noticed that the waves of Rachni on Altahe during the quest UNC: Listening Post Alpha do not offer any XP when defeated. This is a legacy bug that I would really like to see fixed as it would help players more reasonably achieve a higher level by the end of their game.
As you said this was already present in the original games, but it is most likely not a bug.
Regardless if the developers did it for balance reasons or because you have help in the fight by non party members and turrets, it is save to assume that this is intended behavior.
