Aye lad. He's now a right stoofed shirt.
In most all cases with garments, you want to show or imply there is some mass inside it, and then conform the folds in appropriate places like the joints and some of the larger folds. All the while you keep true to the basic description.
Sometimes all bets are off, but that's when one is relying heavily on replicating a photo. As for example skinny bodies will have the clothing hanging more without as much body bulging. And in this lad's case he may have a very loose shirt and he's leaning forward the shirt will hang free. In that case his back would show the form clearly (if we were seeing a profile).
But as a tool, the artist can fake it convincingly by following that rule of thumb you're doing in this case now. Thinking in terms of larger shapes with folds at the stress points is the minimum to communicate to the viewer. Designing drapery/folds can be done beautifully or crudely, but as the Bard says, "The apparel makes the man."
I think here you have improved it a lot, thinking of clarity of info. Well done, Mr. Ploos!
"Not a bit is wasted and the best is yet to come. . ." -- remembered from a dream