Aardvark,
This is a bug that came up in 6.01. Prior to that, your workflow would have been successful. Now, it just doesn’t work. Media manager won’t “shed” the unused media.
We have observed this happening ONLY with multiclips. Here’s our workaround.
Collapsing the multiclip sequence doesn’t do enough. you have to “matchframe” back to the ORIGINAL “non multclip” media and “overcut” it back into the timeline. Be sure to copy and paste any attributes you may have placed on the shot like effects or image changes (motion tab). Delete all of the “multiclip” shots from the timeline. Proceed to media manager. Now, the clips should shed all of the unused media.
Is thys a royal pain in the butt? You bet. But it does work. Use your “feedback button” to let Apple know that fixing this issue is important to you.
Mark