Yes- many digital cameras don't use the full sensor area. It seems they all offer a shooting mode at the native sensor aspect ratio, the LX100 is no exception here (It does do M43 Native). There aren't any 1" or 35mm full frame sensor equipped cameras that don't do 3:2 either.
Im not sure how important/useful maintaining FOV (for the LX100) might be? What is the real benefit of massaging the frames for all available formats into the same image circle so that you might claim FOV is maintained from corner to corner aside from marketing games? The simple fact must be that the angle of coverage across the frame (left to right) can't be maintained. I would think for most this would prove to be the most important consideration.
I appreciate your taking the time here. I know several people who current use an LX100 and while I was aware it shoots 4:3 I wouldn't have guessed it might not be using the full sensor.
You're welcome.
Cameras like the LX100 do not really have a native aspect ratio because it is a multi-aspect camera (every aspect is native) and none of the modes use the entire sensor - so theoretically the sensor could be any shape, provided it was large enough to contain all of the desired aspect ratios at the desired resolutions. It does happen to use a M43 sensor, but that is not necessarily why it has a 4:3 mode.
Maintaining the FOV can be quite useful depending on your personal usage. For example you buy something like the LX100 which has a 24-75mm equivalent lens - being able to change the aspect ratio and not give up any of that range is an advantage. On most other cameras, when you change the aspect ratio you are also changing the FOV. Another example would be on the more expensive GH cameras. If you wanted to change the aspect ratio but the FOV also changed, you might have to go spend thousands of dollars on a new lens to correct the FOV change for video work. But if the FOV stayed the same regardless of the selected aspect ratio, all your lenses will always provide the FOV they are supposed to. Certainly this is not an issue for everyone, but there are advantages to it.
The LX100 II does the exact same thing, but it raises the resolution to 20 MP (maximum 17 MP usable, so it never uses the full sensor either). Another consideration with the compact cameras is that if they did use the entire sensor, the camera, and especially the lens, would be much larger and heavier if they kept the same focal length and aperture. It's still about 1.5X the size of a 1" sensor though, even with it's crops. I actually would have bought one over my Sony RX100 VA if the LX100 II had a fully retracting lens and phase-detect autofocus, but it has neither despite being an outstanding camera in every other way.
As for smaller sensor cameras doing the same thing, the Panasonic LX5 and LX7 both use a 1/1.7" sensor (much smaller yet than either 1" or M43) and also offer the multi-aspect ratio using the same strategy as above.
If you don't care about FOV or resolution, then you can obviously just crop whatever aspect ratio your heart desires into any image. The way Panasonic does it though will always maintain the FOV, but it does bother some people knowing there is a 20MP sensor in their camera and they can only use 17MP