Thanks for the table.

It indeed show that in Japan and China, people on average are about 9cm smaller.

When I was talking of bike size, its indeed what you call extension or what is also called reach.

This is the dimension that is too small on several Tyrell models that are made for the Japanese market.

If you look at the Brompton geometry, you will see that not only the stem height is different but also the stem angle making that S and H type have a longer reach than the M type. The saddle pentaclip allows also to put the saddle a lot to the rear to even increase the saddle handlebar distance (by putting the pentaclip behind the seatpost).

The Birdy (designed in Germany for German people) has not only an height adjustable stem but also two types of stem with two different stem angles and the so called sport stem provides a longer reach.

If it doesn't cause folding problems, having stems with different angles for Helix like for the Birdy would make it fit for taller people.