Okay, maybe you're not interested in a more general feature, but I can't imagine I'm the only Kindle user who might be interested in at least being able to see a column in the Calibre book list that would *show* the collection even if no management of collections would be possible.
Considering existence of the "On Device" column in the Calibre view, clearly there is some "communication" going on; it seems from my position of ignorance that it could also be possible to have an (optional) column in the Calibre view that would show the Kindle collections in the Calibre view when the Kindle is connected. This column, like the On Device column, wouldn't have to permit any editing or management.
I know there are a lot of Kindle users who use Calibre, and most Kindle users use collections. I just came last night from a "Kindle party" where I did a two-hour presentation attempting to introduce Calibre to a large group of friends and acquaintances, all of whom are Kindle users. I explained that they can't manage their collections from Calibre and attempted to explain why, but I have wanted to at least be able to see my collections from within Calibre for a long time (for example, then I could easily create a custom column text column to mirror my collections, in case my Kindle crashes or something) and wasn't able to explain why this couldn't be done. Or are you saying it's not a matter of whether it could be implemented but just that it's a feature you're not interested in implementing?