I assume, like with many renter protections, it's a pain in the arse to actually do in practice, but it's there, so they can't just double your rent in one go to force you out.
Also, rent can only be increased once every 12 months in Vic, so landleeches may need to wait months before they can increase the rent by any amount at all.
Not that I doubt there will be some dodgy workarounds. I suspect landlords might try to abuse the "if the owner is moving back in" exemption, because even if there's strong provisions - e.g. the property can't be advertised again for at least 12 months - it still requires someone to be paying enough attention to notice and report any violations.
How much would it cost the Tenants’ Union to have someone tracking properties on the market and flagging any whose tenants have been evicted over the past year on grounds of moving back in, with a view to suing on behalf of the evicted tenants?
Theres a nice LawTech company in Berlin operating currently where they will take the case for you, in trying to get your rent back to market level, and in Berlin they backpay the difference.
The company Conny.De/en upon a win, take 3months of the rent per month they save you going forward (and in retrospect ).
For older units, Ontario (in Canada) enforces a very low rent raise cap, probably specifically for this reason.
(Alas, for newer units, the conservative government lifted this, so if one rents a newer unit in Ontario (say built after 2018) then one can still be kicked out by this loophole.)
I Qld they introduced laws "banning" no grounds evictions. But here one of the "grounds" is "end of lease". Which has simply meant that every lease is accompanied by an automatic eviction notice, which will be rescinded upon re-signing a new lease. Completely undermines the government's efforts.