As someone who has done this job, I promise you, there’s always another task to accomplish. Normally the cart fetchers are also the store’s defacto janitorial staff, and there’s plenty of cleaning to be done at a grocery store. You are ignorant in this arena.
Why do you think there is always another job to accomplish? Do you think that work magically appeared out of nowhere? Do you think your colleagues are slacking or do you think they had removed a head count from the cleaning staff because the cart staff will now do that role?
Not where you work.
You also failed to answer any of my points. If the head count is 0.25 per hour rather than 0.75, they’ll combine rolls and cut a head count. If 2 roles require 0.75, then they need 1.5 staff and need to round up, if it’s 1.1, they round down and a headcount gone. The shift will be run with 70 staff rather than 71.
How can you work in the role and not know how it works?