"Hey, my phone's out of battery. Can I check my texts on yours real quick?"
B) there's no fine-grained tracking built right in. Extraordinary claims require extraordinary proof. You have the source code to Chromium available to you, please provide evidence. If you believe the visible source code was augmented to add tracking, prior to being installed on the device, then it should be relatively easy to show a Wireshark log demonstrating the fine-grained tracking you speak of.
I thought the whole idea of chromebook was that you used google services rather than locally installed apps. So yes, inherently more tracking since they want to monetise ads.
It doesn't defeat the point for the buyer, since its often the most cost-effective way to get basic hardware for a linux laptop.
It doesn't defeat the point for the hardware vendor.
Heck, it doesn't really even defeat the point for Google. Sure, it may not be as good for them as you using ChromeOS, but its better for them than you either using Windows or MacOS (or paying for Windows or MacOS to get a Linux box.)
The Chromebook is literally no different, in this respect.
So your argument about "inherently more tracking" is fatally flawed.
If I'm watching a movie on my linux laptop and the battery dies I want to continue watching from the same spot on my wife's ipad.
I think Plex media server might do some of that for normal video formats, though I can't see Google and the MPAA being excited about building software to make playing ripped DVDs easier..