Nah i found the same as you, i'm normally an XL or i was in the Nike top but i had to endure the embarrassment of a XXXL with this macron shirt!!
Glad it wasn't just me who found this then! Was XXL not even big enough?!
I found it to be the other way around, I usually wear a medium and the Macron home shirt was really baggy, so a small was a better fit.
Very strange! Maybe it's because I got the long sleeve or something?