A satire shirt that only fits as a billboard is a costume. Buy the size you wear. Heavyweight cotton will move a little in the wash. That is cloth, not a defect.
Size lives on the product and in Support. We will not hide a chart in a footer and call it trust. If you need the human, that is still Support.
Later draft: measurements per blank, hoodie vs tee, and what “M” means when the graphic is huge.