You are correct about the reason for the Done button, but it did not take the position of the Import button. The Import button was always the right-most button, with Cancel to its immediate left. All they did was add the Done button to the left of Cancel.

Now instead of two buttons [Import] [Cancel] they have three buttons [Done] [Import] [Cancel]. And because [Done] is sitting right where [Import] used to be, anyone who has been using the software for years will discover it takes a few times of accidentally clicking [Done] (and muscle memory directs you right to that spot to click it) before figuring out why and how all that time spent setting keywords and on the images was just thrown away when the dialog disappears and nothing gets imported.

Apparently [Done] is so that you can save your import settings without actually importing anything. It’s not a task I’ve ever worried about doing in all of the years I’ve been using Lightroom (I started with v1.0), but apparently enough users wanted that feature that Adobe decided to add it.

So there you have it. Yet another change to the UI without an option to toggle it off / hide it somewhere away from those who don’t really need or want it.