I'm no scientist (like some of you guys are), and I'm no expert in who makes what sensor, but as a Sony user, looking at a lot of D850 RAW files from the web in Capture One Pro, I can say that the way the detail is rendered, and the way the grain and noise structure appears, it doesn't look anything like a Sony sensor.
The files from the D850 are some of the best files I've ever seen out of anything, including MFD. So if it's TowerJazz (kind of a silly name, eh?) then wow, good job to them, and good job to Nikon for squeezing out the detail from it.