I am actually not sure about more weight= less performance.
I dont know how to do the math, there are too many variables like increased air drag and motor load, but this setup actually might offer better performance.
It pretty much ads the area and lift of 2 more propellers to the whole setup, by adding the weight of only 2 props wothout the need of 2 more motors and their weight.
I doubt that the added 2 props weight, spread out on 4 motors is that taxing on the motors, while it does add the surface area and thrust of 2 extra props without the need for the weight of 2 more motors and arms.
I think the advantages coukd outweigh the disadvantages by a big margin.