For me I always like to use the “window” analogy. If you have a smeared or opaque window that isn’t very clear, you can still see the details of the images through it to a certain extent. But a perfectly clear window lets you see the details better than if the window were smeared or opaque/translucent. So in many ways I consider detail retrieval to be image clarity. I think this can come from a number of places experientially, but this is something that I find lets us “peer into the music” better, to borrow a phrase from Tyll.
The other consideration is that some headphones have an easier time of handling that kind of image clarity during busy sections than others. So for example, the high end Audeze LCD planars do a remarkably good job at image clarity during complex layerings and busy passages (try listening to some heavy metal tracks on the LCD-XC for example). It’s really impressive how these headphones are able to keep the image clarity intact, where on many other headphones they have that kind of image clarity for less busy passages, and then things blur together a bit during the complex layerings.
There’s a sense in which this may also all be related to ‘speed’ of the diaphragm - its ability to react to excursive and restorative force, but as many conversations with industry insiders and manufacturers have indicated, if it can produce up to 20khz, then technically it’s moving fast enough. So maybe it’s not precisely the speed of the excursive and restorative force, but more so its behavior related to it. But at the end of the day, it’s still unclear where this kind of ‘detail’ and image clarity comes from, at least from what I’ve been able to identify.