Okay, I did a little research on this topic: It seems as it’s known that GPIO binding doesn’t support restoreOnStartup, comment on Dec 2016 on this bug report from Aug 2016 mentions it: GitHub · Where software is built
There’s an issue for a new GPIO binding with less bugs: https://github.com/openhab/openhab2-addons/issues/1707
There’s even a pull request: https://github.com/openhab/openhab2-addons/pull/1334 - but it only will continue starting in Jun 2018
It will be based on Pi4J http://pi4j.com/ - but with non-privileged acces for GPIO, there’s no PWM: SHA - - - Pi4J Now Supports Non-Privileged Access (no more root/sudo) (which is the next thing I planned to do…)
So I guess, for now the best way to do GPIO is using python scripts like in Control GPIO Voltage