My hunch is that the evolution was driven by executives, probably in the 70s and 80s, that didn’t want to say they were firing people in order to make more money.
In other words the same dynamic that now leads to ‘impacted’.
In other words the same dynamic that now leads to ‘impacted’.
I suspect that in its early versions, it referred more to the notion that "we won't have any more work until the spring, so we'll see you then."
I don't know its etymology or when it might have been coopted by employers who didn't intend to rehire, but I suspect its intent is to signal that there's no ill will between the employer and the employee, and that it WOULD rehire those impacted persons in the future.
I'm not as sure that it means anything so specific now.