I wonder if they may have cut onboard graphics to increase yield by lowering the bar for a QA pass in the lower product ranges. If they are having process difficulties at 10nm, that would allow them to push some of what would normally be rejected to market.
If the GPU part has a failure, you can disable it and rescue the CPU. If the CPU has a failure you might rescue GPU. Pairing failed GPU-CPU's together for cheaper products and selling fully functional ones for the top of the line products makes sense.
The same happens with multi core ships and even with failed caches. Just disable them and sell them as low end chips.
Tegras can get into the 10-15W range which I guess explains why they're now considered automotive processors instead of mobile.
The current Intel 8109u scores about 2x the IPC of the A75 (the main core in the Snapdragon 845). So assuming a generous increase of 15%, the same story as the last 5ish years. ARM is much more efficient; but Intel has more total processing power (especially in the higher power envelopes).