Quoted from razorsedge:"ball saves" existed without auto launch in many games. Maverick is but one example. Also the "home" Whitewater ROM does it just fine. Code simply doesn't launch a ball to the shooter lane if there is one already there.... also back when pinball mostly had Physical locks, instead of an overload of mostly lacklustre imaginary ones... Many games have no auto launch, and a ball save feature.
Many of my fave games don't use "virtual locks" ... they just seem "cheap" somehow to me.
You missed the whole point of the discussion. It wasn't that you can't have ball saves without an auto-plunger. It's that you can't have MULTI-BALL autosave without an auto-plunger.
At worst, the saved balls will back up into the shooter lane. At best, a player could exploit that by intentionally allowing the balls to drain and then plunge single balls - playing multi ball modes with essentially one ball in play at a time.
Maybe you could come up with some weird rule that if there is a "saved" ball in the shooter lane then no other switches will score points or something (and try to explain that to a newbie player somehow), but there are probably ways to exploit that in some way too.
Obviously, in single ball play, there can be ball saves without an auto-plunger. Almost every SS machine made would essentially "ball save" if you scored zero points on a ball. Multi-ball is a different situation.
And if you notice, with your example of Whitewater, the ball save from the home ROM does not work in multi-ball. As soren said, the standard was to do a multi-ball "restart" mode - which is what Whitewater does.