According to that first calculator these are the optimal angles for the latitude of the location of the ZEB house:
I quickly re-calculated this, so may have made a mistake, but with a roof tilt of just 19° you're producing a lot less energy than you could have, even during summer. According to this calculator
the optimal inclination is 46° for this latitude. That's quite a big difference, IMO.
I find this acceptable for an existing structure, but not if you have the possibility to design for optimal energy production. Because this means you'll need less solar panels, and that means reduced consumption of resources. You also don't have to dig energy wells and use all kinds of other high-tech stuff that can break.
So basically this house is oversized (just like Tesla cars), because to appeal to the potential customer and also to allow the engineer/architect to roam freely on a creative level, function must always follow form. And as we all know, sustainability is mostly a part of function.