There is a small correction required to allow the sample : https://developer.apple.com/documentation/metal/deferred_lighting
In order to activate the buffer examination as explained in the readMe file, a change in file "AAPLConfig.h" is required:
At the end of the file, the line
#define SUPPORT_BUFFER_EXAMINATION 1
#define SUPPORT_BUFFER_EXAMINATION_MODE 1
Retrieving data ...