Two different lockers are as common as having them both match. To use one of your examples... a Detroit in the rear works real well, is pretty bulletproof, you don't have to remember to turn it off & on, and it is relatively well behaved. However, a front-mounted automatic locker like the Detroit Locker can sometimes impeded steering enough up front on a tight-twisty trail so you wish you could shut it off & on as needed... which is why some put selectable lockers up front like the ARB.
Other times they put a heavy-duty locker in the rear like an ARB or Detroit Locker but only need a lighter duty/less expensive locker up front like an Aussie or Lockrite. They aren't as strong but for the front which seldom sees more than about 50% of the stress a rear locker can, they are fine for most of us.
So mixes are common, as common as paired lockers are. I've had both paired & mixed lockers and both can be very good choices.