I tried these after seeing the vids.
My first impression is that you really need to feel out your lat and have the "mind connection" to activate it.
I felt it mostly in the rear delts at first (the side portions, not the front pull down portion). Took a few times (and lighter weight) to make sure I could 'feel out' the movement.
Once you make that connection, it's pretty incredible. That was the only thing I changed for that particular back day and I felt it in my lats the next day like I haven't in awhile.
Again, wasn't with a lot of weight at first.