If it's a recurrent linecheck, that's not very likely to happen. I can think of just one that I was aware of and both crew got grounded anyway.

That's what this would be useful for, recurrent linechecks, airlines have to do a lot of them.

From the union perspective we'd prefer to have such no-medical LCA drawn from the ranks of those out on medical disability. Don't really want random line checks from third parties (already get that from the FAA).