Google confirms Android One doesn't require smartphone makers to remove the hiding notch feature
At that time, a moderator from the official HMD forum said the option to hide the notch was removed due to Google's Android One requirements. However, if that were true, then other Android One smartphones should start preventing users from hiding the notch.
The good news is Google confirmed to XDA Developers that Android One does not have such a requirement that will force smartphone makers to remove the hiding notch feature. Fast forward a few days and HMD announced through the voice of its CPO, Juho Sarvikas, that they will enable the setting to black out the notch on the Nokia 6.1 Plus again.
Of course, questions like why HMD removed the hiding notch feature from the Nokia 6.1 Plus and why it said it was required by Google's Android One still remain. But these are questions that we won't be able to answer and the Finnish company will probably never want to admit it made a blunder (if that's the case).
But hey, all's well that ends well, so if you're rocking a Nokia 6.1 Plus, which is a decent mid-range smartphone, then you can expect to be able to hide the notch once again very soon.