At Hoylake for me, the OOB is more about strategy of the hole though I could be wrong.
Jon
Of course, the OOB impinges further into the 16th hole (18th in The Open) than it really needs to, thereby having a strategic influence on the hole, but it still doesn't constitute an internal OOB because it is directly adjacent to the practice ground which is not part of the golf course.
The same situation exists on the 1st (3rd in The Open)
I've played several courses where the practice ground is separated from an adjacent fairway by OOB. A good example is the 16th at Disley in Cheshire.
The tee shot is directly over the practice ground, which is Out of Bounds. Under no stretch of the imagination however, could this be construed as being an internal OOB. The only real difference with Hoylake is that there this situation pertains on BOTH sides of the practice ground.