The nexus program was supposedly short stints of google involvement, like 6 months, basically tweaking something that was more or less already set; so they can change the chip specs and superficialities some, but nothing major. The pixel is supposedly google owned designs, but as we can see they might well've started out with something HTC has some experience with; the bottom area is near exactly like the 10 but with the fingerprint sensor moved to the back. That's what contains the antenna which in modern phones is really tuned so I wouldn't be surprised if they just took it and focused their resources on areas of differentiation.
In any case, IMO their general strategy seems correct, to squeeze apple at the top. There's no point for them to dawdle in the mid-range where android's already won and there's no iphone anyway. The problem is the v1 product isn't quite good enough for iphone prices. It's worse than the price parity samsungs so it's a basically a htc-10-like also-ran product with a google badge. The htc 10's can move some at the 550 it's at right now, which is where I'd expect the pixel to be soon if they want to sell any. Also IMO a bad move for HTC to make something that's only going to squeeze themselves.