It is definitely a thing (see here , here, and here). At one point McQuarrie even sketched a nipple chain under Leia’s tunic, likely inspired by a line Katharine Hepburn has about wanting to wear one in The Lion in Winter.
^sorry , but as an artist who has been in many life drawing classes , there is nothing in these sketches to support your claim . What you are seeing is thumbnails in the first three , devoid of detail and meant to block out a scene,and in the final images ,those are construction lines for building up the figure . Mcquarrie and many other working artists studied anatomy and in order to draw a clothed figure , the underlying structure is first established in order to accurately portray how the drapery falls upon it . Had that been a completely finished painting from that drawing , those lines would not be there .