Bottom line : the average chossid learning the sicha (as I did when I was in tenth grade) understands it like the nefesh Hachaim above. Both because we learn what a Memutza hamechaber is vs. Memutza hamafsik, and also as can be simply inferred from the examples given, all of which are creations expressing / revealing Hashem here.
As far as the Rebbe not having sources- he said he didn’t EXPLICITLY see this written, very different than making it up from scratch, as seen the same idea from his examples.
But as the Rebbe said, you don’t have to accept his understanding. “Yhi lo asher lo.” But do us all a favor and don’t put yourself on the same footing as the Rebbe, especially when you have no clue what he is saying, ie the difference between mimutza hamafsik vs mimutza hamechaber etc. Which is always the case when you misunderstand. Just say you don’t understand. “Bmakom gedolim al taamod.”