Just for fun, I just measured a "real" youth xs, and it's 13.5" wide when laid flat. A small is 14.75" (so, real life measurements, not specs)
That's why, even without any additional obstruction underneath, I go no smaller than youth medium for a full 12-13" design on adult boards.
This "relabeling" by Gildan reminds me of shop I used to work in. the crew neck sweat shirt discovered printed in multi colors on the wrong side for a job since torn down.
They removed the tag and reattached it on the former front.
Gildan's youth tags are almost as wrong!