The TIFF file format is defined as a series of "packets", each identified by a "tag".
Some tags are "vendor defined", meaning those packets can contain whatever data the vendor chooses.
If the TIFF interpreter encounters a packet with an unknown tag, it simply skips that packet,
regardless of its contents, and goes on to the next packet. (see note)
What happens when you choose to open a camera-specific raw file with a TIFF interpreter
is that all of the camera-specific data is simply thrown away.
That does not mean that it doesn't exist. The interpreter just does not know what to do with it, so it's discarded.
This is what the Photoshop error message means.
Note: This is a requirement of any file format that will evolve over time, so it will tolerate and ignore features that are defined in later releases.