I thought the same - that sending an ON should be an ON whether an off was sent first or not. But I do, indeed, have to send an off first. I've tried this both from direct control of the iolinc or with it in as a responder in a scene.
As for my firmware - in an effort to make this work properly I upgraded from 2.7 which was the version I got it with to 2.7.6 which is what it's currently at.
The smarthome manual states that the iolinc can be set up so that an on will cause it to open the door while an off will cause it to close. http://www.smarthome.com/manuals/74551qs.pdf near the bottom says this.
Very confoozalating