Was your sleeveless shirt somewhat of a snug fit? Not skin-tight, but "form-fitting"? If that's the case, the snug shirt and the loose shorts you described, would tend to give the appearance of smaller legs with a larger upper body.
You could try the opposite and see what it looks like. Very loose T-shirt not tucked in, and more form-fitting shorts. My bet would be that the appearance would then be the opposite.
.02,
Joker