It is an open subject and the "Standard" system at the moment does seem to exist in Australia but there are other ways of tackling the problem of sleeping well without buying separate sleeping bags for each season.
I have been working on my own system for a few decades and I still don't think it is perfect and I need to do some more work on it.
But my approach has always been to obtain the maximum versatility with the lowest possible weight and bulk consistent with what I can afford to spend.
My ideal system would be a
1 an UL synthetic overbag with a very breathable but highly water resistant shell a short side zip and a pad sleeve for my
mattresses
2 a lightweight or UL down sleeping bag with an expedition cut with 2.5 inches of insulation weighing less than a kilo
3 a down half bag with 2.5 inches of insulation weighing less than 300 grams
4 a down parka with the same 2.5 inches of insulation [ OK 2.5 inches on the torso and an inch on the arms and head ] weighing as little as possible but as close to 500 grams as possible
What I have is as above but without the mattress pocket and all much heavier than the wish-list weights
My Shell overbag weighs almost a kilo and a half; my Expedition cut sleeping bag weighs 1155 grams The Western Mountaineering Tamarack weighs 540 grams because of the long heavy duty zipper and my old Everest parka weighs over a kilo but is Very very warm
What's your own ideal sleeping system to cover tha whole range of temperatures from high summer to deep winter?