I agree with Livvy, I can't imagine sitting on bricks for more than 15 minutes
It looks interesting though and I'm sure that it's easy to build it.
Fifteen minutes!?
I wouldn't even last five. It's going to have a straight up back, so you'd have to sit perfectly right angled. Which is painful enough, even if the whole thing wasn't made out of cinder blocks to begin with! I'm sure there could be a lovely little thing made out of bricks, as long as you constructed it a bit differently.
I mean, keep the sofa's basis structure the same, only make a sort of pit on the top there. Fill it up with cushions/comfy things, and do the same to the back as well. Boom! Comfy brick sofa. Oh actually, you could make this even more garden friendly and use some sort of plant in place of the cushions! Maybe moss for example?