While appreciating Apple’s note, it wouldn’t take a rocket scientist to come up with that conclusion alone.
There are, however, sticky sliding covers which are very small and very thin so they fit well into the very thin bezel of the MBP16, and while still protruding above the surface of the glass, they do not add more than a quarter of a millimeter to the distance between the glass and the metal surface when the lid is closed. I have found that there is more than enough flex in the glass and cover to accommodate that.
As for the Lenovo solution of a built-in slider - there’s a catch to that: The camera is very thin as it is. Thin means poor quality. “Camera” means “room”, and that’s the distance between the lens and the image sensor. Thinner cameras means shorter distance which means poorer quality. That’s not the full scientific story behind photography but sufficient for this discussion. When you add the slider that means there is less room for the camera which means an even thinner camera and thus - poorer quality. If they make it much thinner they quality might be so bad that you won’t even need a cover anyway.
On a side note, with COVID-19 travel bans my laptop had become a desktop and I haven’t closed the lid and packed my MBP for about 5 months so the problem is self-mitigated until travel is resumed…