The other idea is simply about putting forward an anarchist position within a union, that is not the same thing as attempting to lead it.
Nick Durie is one individual, his article on the L&S site is also irrelevant to this debate - it would not preclude a hypothetical organisation that adopted his pov in the current climate working within a hypothetically existing AS union, they would naturally change their pov to take note of changed conditions.
the point is Nick's approach is internally consistent and historically grounded. i think it's misguided (e.g. even promoting anarchist strategies within the trade unions i would argue is better pursued by industrial networks), but it is coherent. it's not just hypothetical a-s unions, even the relationship of political groups to something like SolFed with one or more industrial networks is unclear. i'm open to persuasion that they're compatible, but you have to make the case. Nick Durie makes a pretty good case why they're not.