I've only been casually watching this, and not attempting to solve the puzzle, but I am tending to view this in terms of TD.
Not all of the twenty-four-hour shift is "work", unless called out, right? Some of it is, yes, but some is also spent simply sleeping in a bed other than one's own. I frequently spent a fair amount of one to three days of TD, sometimes several times a month, during my early flying career. Each of the middle days represented a twenty-four-hour "shift", and the first and last day well more than the normal eight-hour workday, if one factors the sleeping-in-a-bed-other-than-one's-own aspect in. We never received additional time off for that, nor should we have.
I don't begrudge a shiftworker a little extra time off for the inconvenience of working evenings/nights/weekends and missing family time or living with disrupted circadian rhythms for a few years, but the shifts in question do not appear to do that - too much, at least - unless routinely called out over the full shift cycle. Even then, there appears to be full twenty-four-hour period for recovery and own-time after each.
A fair and consistent means of determining leave remains necessary, but I have no real idea what that would be.