Actually that picture overdoes it a tad...
The absolute minimum to avoid chronic nipple separation of the barrel from the head is for the spoke end to penetrate the thickness of the rim AFTER proper tension has been achieved. You can be 1.5mm below the screwdriver flat of the nipple and you'll be okay - that is if you don't mind seeing a thread or two when using 10mm/12mm nipples.
In most cases though, the spoke end is barely reaching the edge of the rim - often the case when manufacturers are using 16mm nipples on standard 9.0mm threaded boxed spokes. Very common with the factory machine built DP-18s on Formula/Origin8 track hubs.
Use a flashlight - take a peek - if you think the spoke ends are down deeper than a 2mm - a rebuild is called for with the proper length spokes.
Nipples are nipples - they're not meant to be spokes.
=8-)
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life