Thats actually not accurate for the AA WO's. Their AA interview was to enter the pipeline program in college, or when they started at an AA owned regional. When their seniority number gets called, they flow to AA as an intercompany transfer. Non-pilot seniority benefits transfer over as well, just nothing pilot seniority wise. The only way to not go is to have too many step letters in the previous year. Thus far, I've not heard of anybody being denied flow. AA decides on the letters, not the regional, and AA HR knows the regional managers pull that bull****. They ignore it for the most part if it's stuff like sick with Dr.notes. To them that is a legitimate sick call and shouldn't be in your file. They advertise it as 1 interview, cradle to grave.
now, if you're bending metal, that's different.

the other non owned contractors have an unguaranteed flow. They can, and do, find any reason not not flow them when they have enough qualified street applicants.