You can read more about our our editing model here – you may want to read the whole thing if you have some time, but the relevant section is entitled “3-Layer Editing Model”.
There are some editing functions we don’t support over a certain number of selected tracks – for example, there’s no way to set thousands of tracks to be “live” at once. That tab is only available for editing up to 1000 tracks at once.
As discussed, in this case it’s unfortunate that the original import dates were tracked in a way that was susceptible to storage device changes. In certain cases, this long standing bug could cause content to be re-imported.
The good news is that this issue has been resolved, and in the vast majority of situations, the fix should make this kind “re-importing” impossible, so apologies again for the trouble.