Recently picked up a Pixel Slate and been using the Android Onenote app and I've noticed some weirdness that I think needed to be addressed by the team. The main thing is that even though they are the same version number, Onenote for Android phones (my Pixel 3) has Sticky Note integration while the tablet version for Android tablets/Chrome OS doesn't. It seems to have an older design too versus the Android phone version. I would try and sideload to see if the apks are different but you can't do that yet on Chrome OS. But I think it would be useful to update that tablet interface to at least match what we see in the current iPad version of Onenote.
Also when using a keyboard and mouse, unlike the other Android Office apps Onenote doesn't allow you to double click to highlight words/lines of text or right click to take action on them. That's a huge problem that I hope the Onenote team can take care of for us.