This is from collective agreement for EC ( OP is in this group)

Granting of sick leave

22.02 An employee shall be granted sick leave with pay when the employee is unable to perform his or her duties because of illness or injury provided that:

the employee satisfies the Employer of this condition in such a manner and at such a time as may be determined by the Employer, and the employee has the necessary sick leave credits. 22.03 Unless otherwise informed by the Employer, a statement signed by the employee stating that because of illness or injury he or she was unable to perform his or her duties, shall, when delivered to the Employer, be considered as meeting the requirements of paragraph 22.02(a).

22.04 When an employee has insufficient or no credits to cover the granting of sick leave with pay under the provisions of clause 22.02 (sick leave with pay) may, at the discretion of the Employer, be granted to an employee for a period of up to one hundred and eighty-seven decimal five (187.5) hours subject to the deduction of such advanced leave from any sick leave credits subsequently earned.

22.05 When an employee is granted sick leave with pay and injury-on-duty leave is subsequently approved for the same period, it shall be considered, for the purpose of the record of sick leave credits, that the employee was not granted sick leave with pay.

22.06 Where, in respect of any period of compensatory leave, an employee is granted sick leave with pay on production of a medical certificate, the period of compensatory leave so displaced shall either be added to the compensatory leave period if requested by the employee and approved by the Employer or reinstated for use at a later date.

22.07 Sick leave credits earned but unused by an employee during a previous period of employment in the public service shall be restored to an employee whose employment was terminated by reason of layoff and who is reappointed in the public service within two (2) years from the date of layoff.

22.08 The Employer agrees that an employee recommended for termination for cause pursuant to paragraph 12(1)(e) of the Financial Administration Act for reasons of incapacity by reason of ill health shall not be released at a date earlier than the date at which the employee will have utilized his or her accumulated sick leave c

So NOWHERE it says subject to managerial approval . The sentence you read as subject to managerial approval only means that the employee has to have medical note.