There's also this very plausible theory that Maxwell only existed because of the cancellation of the 20nm node.
NV's prior road maps did not have Maxwell. It was a Kepler -> Pascal leap.
This theory propose that Maxwell is Pascal, with most of the FP64 stripped, mix-mode ops stripped, a purely gaming or FP32 focus design. This results in the nice gains versus Kepler, at the same 28nm, despite only small die size increase (GK104 -> GM204 etc), NV has extracted a lot of performance from it.
Now, if that theory is true, the real comparison for Pascal should be made versus Kepler.
We're talking GK104 vs GP104, and GK110 vs GP100. What kind of performance leap is that? It's a massive perf leap.