It's very standard under the Canada leave provisions with respect to leaves that someone who is seeking leave indicates to their employer the purpose and the duration of the leave. In the particular case of family violence leave, under the proposed changes an employee would need to indicate that they wished to take this particular leave, and in proposed subsection 206.7(2), the specific reasons for which the leave can be taken are enumerated. Those are things like seeking medical attention or obtaining services from a victim support organization.
To be eligible for the leave, the employee needs to indicate the reasons. Nothing requires an employee to provide any more information. They just need to say they need to seek medical attention or they need to take their child to their family physician to seek medical attention.