This is intentional. The problem with the "add to outfit" option is that when locked items got kicked in the process, they must be reattached, and reattaching them too quickly makes them loose the changes they went through before being detached (and most notably the scripts states). This is because of a well known SL bug
Marine then decided to disable "Add to outfit" and "Replace outfit" while at least one item is locked on your avatar.
The Cool VL Viewer works around this problem for "Wear", by starting a timer (configurable via a debug setting and defaulting to 15s) and reattaching the kicked item only after the timer has elapsed, thus not triggering the bug. However, this method won't work for multiple kicked attachments (since you never know when a given attachment is actually kicked by another that just rezzed: this depends too much on lag), thus why I didn't re-enable the "Add to outfit" and "Replace outfit" options. These will only be enabled after LL fixes this nasty bug of theirs.