It's really not weird at all, pretty much all high end phones use sensors from Sony because they make the best sensors for this specific application. Some of the phones I know of that had the IMX377: Nexus 5X Nexus 6P HTC One M10

It looks like the Pixel is using the IMX378 -- I'm not sure what differences there are between the IMX377 and IMX378.

It's also worth noting that there is a lot more that goes into a good camera system than the sensor

Apple, Samsung, HTC, LG, OnePlus and Sony all use sensors from the same manufacturer for their high-end models (and often just the same sensors). They're all Sony.

Well, like someone mentioned above, Sony is really dominating this market with its sensors. Which means it's not that strange to have a bunch of similar sized and prices phones use the same sensor.

They've been using the same SoC, memory, etc for years. To your point, it would be interesting to see a breakdown of how much the major Android phone manufacturers actually use unique hardware.

Mainly going by the camera specs: 12.3MP, f/2.0. And it "makes sense" for a phone maker to use the same sensor for two years in a row. At least I know Apple does that (sometimes even keeps it for 3 years, like it did with its first 8MP camera).

I think it would be weirder and less likely if they ordered a "next-gen" camera that had exactly 12.3MP resolution and f/2.0 lens, just as last year's camera. There's still a small chance I could be wrong, though, so just take it with a grain of salt. Perhaps Google will confirm it either way soon.