When you consider the recent lookbooks, and the fact Supreme gets so much attention from young teens it is a bit weird why they still hardly ever have smalls in the west.Because Jebbia is being smart. This is exactly what he's trying to avoid.
It must just boil down to the production numbers. Japan has 5 or 6 stores + web and the general population there is short and slim so they automatically get 98% of the smalls. It's like Supreme isn't taking into account to make more for the west or just too lazy/blazed to even notice.
That being said all the CDG stuff from this season was available in the US and UK in size small, along with PCL tee + hoodie, Crosses tee, Kingston tee and probably a couple more. Still, It's not a great deal when you consider how many other pieces dropped.