The article says “At LEAST One... submaring left port”... so the other five could not leave under their own power and each seems to have a tug towing them (or pushing them along then separating for the two “in line” photos). That it?
Or maybe they are Alphas from long ago, now all rusting in the graveyard— and this is a really old photo?
Correction— submarine not submaring... sheesh.