This is not true. What matters is that it meets the chickens' needs. The chickens won't care if it's professional or DIY, if it's pretty or ugly. People fall for the professional trap often, order these beautiful coops made by carpenters, that are inadequate for chickens, because the profession...
Two wrongs don't make a right.... You'd just have two crappy pseudo-coops, the two together won't make a real coop. If you haven't gotten the chicks yet, seriously consider 3-4 bantams instead. It's not fair to the larger birds (especially giant) to cram them into that dollhouse. A lot of people...
I agree with Dobielover too, that's way too small. The run might do, but the Eglu is tiny. Maybe 2 LF chickens max, 5 is too many especially if 3 of them are giant. It's not worth it. Consider getting bantams instead, or a real coop.