"ZBook Studio. Clearly competing against Dell's Precision 5520 (and in nearly all ways, surpassing it)"
That's not true at all, in fact, if you must compare, the 5520 is actually few steps ahead. But that doesn't matter, because there's absolutely no reason to buy these overpriced "lighteweight workstations" that don't even have ECC support or high end graphics.
There's plenty premium consumer laptops in the 1.5~2kg range, that come with 1050/1050Ti graphics that are simply better in price-performance ratio. Beginning with better known "all-around multimedia" laptops like XPS 15 or Zenbook Pro to budget gaming laptops from ODMs such as Gigabyte Phantasus, Aorus, Clevo, MSI, Asus, Eurocom, etc. That is of course, if you're willing to compromise a little of battery life and build quality.
Either way, the only major highlight for 2017 workstation laptops is the inclusion of (1070 equivalent) P5000 graphics with whopping 16GB of VRAM and VR support.