When they say this shirt provides "generous" freedom of movement, they are not lying. They are being a bit euphemistic, and understating the truth.
At 55yo, I know what size shirt I wear. Medium. This shirt is attractive & well-made, but is HUGE, if indeed this IS actually a medium, as the tag claims. IMO, the legend should say that this items RUNS LARGE, or to adjust the sizing chart accordingly. Dry clean only, my eye. I hope to be able to shrink this into submission. Short of that, I will (re)order this in a Small.