I know it's only my 2 Cents, however I did lose almost half a Size on an 18Oz OD CPO Denim Shirt with a really hot Bath Soak (60° + with Woolite added and agitation).
This Denim also was not meant to shrink with having been through the aggressive OD process but sizing definitely went down across the board.
This was on an XL that was just a little loose. And final dimensions were almost right bang in the middle between L and XL averages which worked out to perfection.
The Woolite heped ensure no real colour loss.
Hope this helps.
Mark.