You're arguing with straw men. No one has insisted on the 128-bit bus, just that it was a possibility based on the design of Parker that was originally shown almost a year ago now. We also don't know how early the dev board was that Eurogamer described as running the Tegra X1, as the description of it sounded a lot like a Jetson TX1 development board with it's noisy cooler and running hot as the sun. It's very possible that the Switch is running a customized version of the X1, but there would be literally no benefit to Nintendo for doing so, as Nvidia has known since 2012 that 20nm was a failure and a dead end, and would have pushed them towards 16nm when attempting to make this sale. They had internally abandoned 20nm prior to when Iwata first announced that the NX was in development, and really only continued forward with the X1 because they had made contractual commitments to TSMC and High Power chips on the node were a total failure. It wouldn't make sense for them to try and push the X1 on Nintendo at 20nm long term, especially if they had limited quantities that would quickly deplete if the Switch is a success.
We also had rumors from people here on the site (NateDrake), who asserted that he had a source he trusted that told him that the final hardware of the Switch would run a newer chip than what was in early Devkits. The speculation about ESRAM or additional cache setup is conjecture based on Nintendo's history of spending a lot of money on fast memory, even when seemingly going cheap on other components.
As Thraktor posted earlier, there is advanced memory compression and tile based rendering in place on the Nvidia card that isn't in place on the AMD chips in the other consoles. That doesn't magically make up the chasm of a difference between the power envelopes in play here, but it means that the Nvidia chip will punch above it's expected weight. There are also proprietary Nvidia Tech like Multi Res Shading and their proprietary tools and API's for Vulkan (including speeding up the importation of DirectX assets) that should make the Switch and attractive platform to port to from software that started on PC.
Lots of reasons to be optimistic, at least for ports. I don't think anyone sincerely believes the Switch will be as powerful as the Xbox One or PS4, but it should be able to run competent ports if all the technology is leveraged.