There may be a substantial difference, whether you use this substitute directly or indirectly. Used directly the Ammonium Thiosulfate probably doesn't hurt at all, whereas it could make indirect toning a gamble.
As I always used it directly, that was never a question to me. But if you want to work indirectly, you can just split the steps and never join the components for sulfur and selenium in the first place which also adds some more freedom which to some may cause insecurity whereas others just squeeze it until it's lemonade.