That used to be true until they found a way to shave down the cartilage on the Adam’s Apple so it doesn’t protrude.
My take? The hands and the shoulders.
Women have more rounded fingertips and men have more square fingertips. Plus men’s hands are bigger (also related; wrists). A lot of them know this and wear fake nails and bracelets to cover it.
Even for a guy with a twink body shape, you can still tell the difference in whether the shoulders are more square or rounded (as they are in women).
They have surgeries for damn near everything now but I don’t think anyone’s willing to fuck with shaving shoulders or feminizing hands/wrists (yet).