On the early 2.5 turbos after Subaru had problems with banjo bolt screens clogging, and required all turbos as "severe service", they explicitly recommended against oil extractors on those engines. They felt that there were too many deposits left at the bottom of the oil pan that were not extracted. This is from an article that appeared in Drive magazine.Is anyone using an oil extractor on the 2.4? That's pretty normal on marine engines where you can't get under the engine. If you're DIY changing your own oil frequently, it's not the end of the world if you don't get the last bit of oil out.
Carbon deposits produced by a turbocharged engine can accumulate at the bottom of the oil pan. When changing the oil, always drain the oil through the oil drain plug hole on the oil pan. A vacuum draining device could leave carbon deposits in the oil pan and potentially contaminate the new oil.
How To Care for Turbocharged Subaru Vehicles | Stanley Subaru
I know that some manufacturers even recommend them but Subaru's are extremely easy to change oil on so I don't really see a benefit. On the other hand, maybe the fuel dilution in the oil from these DI engines keep the deposits from accumulating at the bottom of the oil pan.