I have a problem with the way this works since the update too. From reading the release notes the intended behavior is for photos to remain in "All Synced Photographs" even when sync for the collection they are contained in is turned off.
With the previous behavior, if I had a collection of photos synced with Lr Mobile and I no longer wanted them to be synced with Lr Mobile I would uncheck the sync box next to the collection and they would no longer be synced. This makes sense to me and makes it easy to see what is synced and to selectively sync some collections and not others.
With the behavior after the update, if I uncheck the sync box because I no longer want to sync that collection then I still have to go to "All Synced Photographs" and figure out how to select just the photos from the collection I don't want to sync anymore and remove those as described by @greule above.
This really doesn't make sense to me and I would like to understand the reason behind having the photos remain in the "All Synced Photographs".
Even worse!!! If you delete a photo from "All Synced Photographs" and it's still in a synced collection, that photo is removed from "All Synced Photographs" AND from the synced collection on the desktop. This has to be a bug, right?!!
Actually, the "problem" manifest itself using the desktop version.
greule i think the correct behaviour could be to show that dialog not only when clicking the menu, but also when using the B hotkey (remove from target collection), and when clicking sync/unsync on the collection itself.
Also, the user could be given the option to select NO as default option and don't show the dialog again, what you think?
Have you tried the "Don't show again" check box? - Guido
Actually, i didn't because i was wrongly assuming that "don't show again" would default to "yes".
I tried it now and of course i report it works correctly as you kindly suggested, thanks a lot!
so, in my opinion, the only missing part is having this works correctly also if the action is triggered by the target collection hotkey (B)