The WRX 2L oil pan has been the one from back in the day. It's even on the EJ25D. The reason for the change on the STi oil pan is to clear the twinscroll header, which we don't have. Even the NA Subarus have the same pan now because of the design of the na header. Subaru can discontinue the 2L oil pan because it no longer needs to make them when all the newer cars run a header that wraps around under the engine, excluding the front facing turbo models. I wouldn't be surprised if the dealer required you to purchase a package of the newer pan, pickup, and windage tray with dip stick when going to buy a 2L oil pan.
The 2L has good control of oil sloshing around. Fill up the pans with a gallon of water and see how the baffle is placed. It's very open on the STi pan. I don't see issues with oil not being able to get into the pan. The 2L baffle tray is cupped up, but is NOT flush with the pan all around. The heads have little to no issues with oil flowing back through the block into the pan area. In turns of high lateral g-force it doesn't matter how good a pan you have, you'll have to be on the straight for oil to drain back towards the pan area.
Both pans are tilted slightly back how it would be on the engine.