ooops ....
would be interesting to find out where you got that fork, as I am looking, begging etc etc to get some myself. You can pm me with the aanswer :-)
You are right Terns and Dahon bikes like the jetstream have a longer headtube...pretty sure the mu models as well..... most others have a shorter ones
I have some suspension forks coming my way and those have a longer steerer to fit both :-)
Best Thor