Not being covered if no leave pass

[Eye In The Sky]

Makes sense.

Is there any authority I can go to confirm this? Does a superior commander need to officially establish that the unit is working under a shift-work structure? Can the CO make that determination?

Actually, it is defined in the Leave Policy Manual and I quoted it above...

1.1.22 Shift worker
A shift worker is a person who does not necessarily have a working day schedule of Monday to Friday with Saturday, Sunday and designated and/or statutory holidays scheduled as non-working days.

Our Sqn Orders, signed and published under the CO, designate who is/is not shift workers..so, in (parts of the) RCAF the authority is the Sqn/Unit CO vice Wing Comd or Div.