Update: HMD officially stated that the option will be back. More here.
With the latest August update for Nokia 6.1 Plus, Nokia Mobile removed the option to hide the notch, which caused quite an anger in the online community. At First, I thought that it was just a mistake from HMD (wouldn’t be the First), but it seems that the option to hide the notch was intentionally removed by Nokia Mobile.
To make the situation even worse, the feature, allegedly, wasn’t removed because HMD likes the notch so much and wants to force everyone to use it, but it was removed because Google requested it. The “hide notch” option probably isn’t a part of the “Pure” Android One experience and had to be removed.
This info comes from a moderator at Nokia’s Community Forums and we can regard it as official. I have no idea why Google has anything against such an option, and if Google really intervened because of a simple option like hide the notch, HMD should think of exiting Google’s Android One program and optimizing the China ROM (with much more software features that are available for Nokia phones in China) for the global audience.
Source: Nokia Community Forum