You cannot use the share function to share an editable iMovie project from your Mac using AirDrop. In fact, you cannot share an editable iMovie Mac project to your iPhone using any method. You can share an editable iPhone iMovie project from your iPhone to your Mac using AirDrop. Perhaps that is what you are recalling.
Since your iMovie project is on your Mac, what you can do is share it out to a movie file on your desktop, and then use Air Drop to send it to your iPhone. Then you can import it into iPhone iMovie and edit it to a limited extent as if it were one big clip.
-- Rich