The Pixel C, on many dedicated technology websites, is being compared to the iPad Pro and Microsoft's Surface range of devices. First, as posted before, it is a mistake to compare the iPad Pro to the Surface devices. Similarly, it would be a mistake to compare the Pixel C to either the iPad Pro or Microsoft Surface and Surface Pro. A docked tablet, for enhanced productivity, is nothing new and I don't believe Google intends this to be something different, in that way (docked Android tablets was first made mainstream with the Asus Transformer range). Nevertheless, it can be stated, that the metallic keyboard dock released by Google is genuinely its own product, compared to other manufacturers.
The Pixel C is part of Google's Pixel range, in which full ownership is taken for hardware and software. The Nexus range of products, on the other hand, are partnerships with other manufacturers, with Google taking ownership of the operating system. There is also a difference in purpose - the Pixel devices are more experimental, while the Nexus ones are more finished consumer products. Further, Ron Amadeo, at Ars Technica, may be correct in his speculation that this may have been an experimental Chrome OS convertible device; however, where he goes wrong is to point to the mismatch between hardware and operating system features to then buttress his speculation. I believe this mismatch is intentional and is consistent with what Google aims to showcase with the Pixel products. In other words, the Pixel range is meant to show the potentials of Android and Chrome OS, as is the case with the Chromebook Pixel - the Pixel C is just another example. Further, there appears to be a design in the the current mismatch; for example, from aspect ratio to four microphones, the idea is to future proof upcoming features such as enhanced voice recognition to split screen multi-tasking.
To sum, this isn't meant to be a productivity device compared to Apple's iPad Pro (Apple explicitly markets the iPad Pro as a possible laptop replacement) but is part of Google's attempt to develop both hardware and software, in-tandem, with the Pixel range being an experimental showcase for Android's future direction. Even with this experimental ethos, it can still be argued that the Pixel C, at this moment, is the best Android tablet out there and one that will only get better with future updates