As far as I know all cameras do this, including your previous Panasonic Lumix cameras. The camera produced JPEG preview that is attached to the raw file will be in the instructed aspect ratio, but the actual raw image data will contain all of the information collected by the entire sensor.
The following is an excerpt from my answer to Why can software correct white balance more accurately for RAW files than it can with JPEGs? which you may find helpful:
Anytime you open a raw file and look at it on your screen, you are not viewing "THE raw file." You are viewing one among a
near-countless number of possible interpretations of the data in
the raw file. The raw data itself contains a single (monochrome)
brightness value measure by each pixel well. With Bayer masked camera
sensors (the vast majority of color digital cameras use Bayer filters)
each pixel well has a color filter in front of it that is either
'red', 'green', or 'blue' (the actual 'colors' of the filters in most
Bayer Masks are anywhere from a slightly yellowish-green to an
orange-yellow for 'red", a slightly yellow green for 'green' and a
bluish-violet for 'blue' - these colors more or less correspond to
the center of sensitivity for the three types of cones in our
retinas). For a more complete discussion of how we get color
information out of the single brightness values measured at each pixel
well, please see RAW files store 3 colors per pixel, or only one?
Here's a similar example where the shooter chose B&W but when they opened the raw files on a computer they were being rendered in color. When the raw data is saved with the camera set to 'Monochrome' or 'B&W' the preview image will be a B&W image, but the raw data will still contain all of the information collected by the sensor which can be used later to render the images in color. When the raw data is opened in different viewers or conversion applications, some will use the JPEG preview and display the B&W image generated in the camera, some will read the 'B&W' instruction in the metadata to create their own B&W rendering, and others will totally ignore the B&W instruction and apply their own default processing instructions that will display a full color image.
When you view "raw" images, you're looking at a very processed interpretation of the information collected by the camera and stored in the raw image data.
- Some raw image viewers or raw processing apps will display the attached JPEG preview, in which case you will see the selected aspect ratio when you took the photo.
- Other raw image viewers and conversion apps will do their own conversion of the raw data to produce one among a near infinite possible interpretations of the data contained in the raw file. How close this interpretation will be to the preview JPEG produced by the camera (or a JPEG produced by the camera if you saved Raw + JPEG) depends on how close the processing instructions used by the rendering viewer or app are to the processing instructions used by the camera to produce the preview image.
The instruction to use a certain aspect ratio is stored in the raw image file's EXIF Info that is part of the metadata included along with the actual data collected by the image sensor.
- If the viewer or conversion app reads and applies this instruction then they will also display their interpretation of the image in the same aspect ratio.
- If the viewer or app ignores this instruction, then they'll probably display a conversion of the full 4:3 image.
Sometimes the aspect ratio instruction may only be stored in a section of the EXIF Info known as the "Maker Notes" section. This section allows camera makers to store whatever they want in whatever form they want without having to comply with the standards that govern how the standardized fields in EXIF Info are defined.
For example, there's only one correct way to record "f/5.6" in the standard 'Aperture' field of the EXIF Info. Every manufacturer uses the same hex code to mean "f/5.6". The same is true for all other f-number values, all exposure time values (shutter speeds), ISO settings, etc. There is a standard way to record those values that is set out in the EXIF standard.
Information in the 'Maker Notes' section is not standardized. A hex code used by one manufacturer for a field they created to record something like "Lens Maximum Focal Length" may mean "500mm". The same hex code used by another manufacturer in a different field they created to describe a different thing, such as "Flash Exposure Compensation" may mean "-3EV".
Many raw image viewers and raw conversion apps do not have the needed information to properly interpret the 'Maker Note' sections of the EXIF Info from many cameras, so they ignore it. Adobe, for instance, has adamantly resisted using any 'Maker Note' information that they don't absolutely have to. When you export an image from any Adobe application, the 'Maker Note' section is stripped from the EXIF Info and not included in the exported image.
