You are right that you must complete the wind-on to cock the shutter before the lens can be retracted - just raising the rewind knob to disengage the sprockets won't do it. But you can't wind on when the rewind lever is up! So I think the only way to get the lens in is to finish the rewind process, put the rewind lever down again, then do a wind-on (with or without a new film in place). You can watch the mechanics when the camera is empty.
Incidentally, to the OP: film loading in these cameras is as simple as it gets. Shove the leader in beside the arrows, use your thumb on the knurled bit of the uptake spool until the sprocket teeth engage. Flip the pressure plate back up, slide the back cover on (you sometimes need to squeeze the top edge into place gently), and you're good to go.
And ain't that viewfinder just lovely?