There are a lot of good oil separators on the market, as Asphaltgambler said above, google to find a good one for your application. For me, its cheap insurance.
Also, I'd thought the Subaru DI engines also used secondary port injection in part to wash the valves.
https://www.caranddriver.com/news/explained-why-some-engines-have-both-port-and-direct-injection
https://oppositelock.kinja.com/state-of-the-flat-4-us-my2017-1794660042
Maybe just the BRZ ??