The small group of programs who will be requesting the self-identification questionnaire as an optional document in their program descriptions have explicitly highlighted equity, diversity and inclusion as selection goals, and they have stated exactly how they will be using the information collected through the questionnaire in their selection processes.
These details are available within their program descriptions. Specific questions should be directed to the program.
If you apply to these programs, it is entirely your choice whether you want to provide the questionnaire as part of your application package. This is your information, and you have complete control over who it will be shared with.