I mean, look at this UI: The selections look like just labels, not buttons, both have the same width border, same background, same size, and the ONLY difference is that one border is gray and the other is black.
And then I didn’t look closely enough during checkout because I was already stressed out and rushed. (RTS: don’t buy things online when you’re in too much of a hurry to double check the checkout.) No shipping charge, so 🤷♂️
And then the email & website said NOTHING about the medium.