You’re a bit confused here. A Subaru is AWD, and essentially has 3 diffs. Centre, front and rear. A Tacoma has 2 diffs. And a transfer case in the middle. A transfer case acts like a locked centre diff when engaged in 4wd, otherwise only sends power to the rear diff. When 4x4 people talk about locking diffs they mean a locking front and or rear diff.

Something like a wrangler rubicon or a G-class would have a locking front and rear from factory which is rare. Transfer case and locking rear isn’t particularly unusual in an offroad vehicle.