those are not ride height adjusters... those are spring preload adjusters... while they may happen to affect dynamic ride height, that is not what they are.
Sorry, but in the case of a 919 with its very short top out springs, in the normal operational stroke zone, the adjusters change ride height and do not change the compressed length of the spring, nor the stored energy, so can't be "preload" adjusters.
The evidence is the fact that when you turn them in, the bike lifts up upon the springs by the same amount, while the spring remains the same length. So, seeing as the compressed spring length remains the same, the top out spring has not been engaged, the stored energy remains the same, then the only thing that has changed is the ride height, therefore a ride height adjustment was made, not a preload adjustment. So, when one plays with the adjusters, the only thing being changed is front end ride height - the sole exception being the net effective spring rate near and at full extension when the top out spring starts to be engaged.
I see the use of the term Preload Adjusters re the front of the 919 is somewhat akin to at least one manufacturer referring to their low "speed" ("fork stroke velocity") rebound adjuster screw to being a Tension Adjuster, and marking their adjuster with a "T". Hmmmm, low speed rebound adjustment alters the damping force characteristic of the rebound hydraulic circuit when the fork begins to decompress and re-extend due to compressed spring force energy. Where is the "Tension" in that?