Not sure if it`s a bug or not or some game balance decision before release, but Imperials give only +1 influence. On the official site it`s written +1 inluence, +1 influence on temperate planet. 

Yep it's a balancing decision (and not a bug) :)

The wiki needs to be updated but I presume this will be done later, once the larger balancing changes will have been made.

Cheers,