[broadgage]

SWER is indeed used in Australia, but only for the high voltage supply into distribution transformers.
Half wave rectification of the mains would have no effect on the high voltage circuit feeding the power company transformer.

It would however adversely affect the transformer itself, DC current through the low voltage side of the transformer would tend to saturate the core and result in extra heating and losses.
A small transformer for a single household would be more vulnerable than a large one in a built up area.
But we have single transformers for isolated homes here in the UK, and no one worries.

Of greater concern would be higher loading appliances with half wave rectification. Hair dryers and the like. I suspect that no one has realised that these are sold worldwide including presumably in Australia.

There is somewhere a now long closed thread in which I enquired about the effects of half wave rectification on power company transformers.