In fact, I was thinking about the use case of a virtual encrypted disk within a file. In this case, my guess is that the OS knows the file in which the virtual encrypted disk is. But when veracrypt opens the embedded virtual encrypted disk, I suppose that it is using an encrypted descriptor to know the size of the virtual encrypted disk. And, in this case, it could handle 2 descriptors of the virtual encrypted disk, one when the password of the innner encrypted disk is provided and one when it is...
Wouldn't it be possible to provide to the OS the area dedicated to the outer volume when the inner volume protection is activated (for sure, without the inner protection activated, the whole volume (outer + inner) would be seen by the OS to allow the plausible deniability) ? This would allow to use the outer volume as a regular volume without the risk to corrupt the outer volume as specified in the documentation ? Is this technically impossible ? What would be the risks of this behavior ?