Doesn't matter if you updated or not, obviously your HBOOT was 3.18 prior to updating, which basically means that you didn't have any options anyway unless you updated twice or more. This method, simply put, was for all HK users still on 4.4.2 KitKat, if I remember correctly then your HBOOT had to be 3.16 for this to work. Sunshine will include support for 3.18 and 3.19 HBOOT's in the 3.0 release but that's only happening after a month or something. No precise ETA was given for obvious reasons.
If I were you I'd steer clear of this thread and the instructions mentioned in the first post. As I said before, chances are that someone might just end up bricking their device for good if done something wrong. As an inexperienced user myself and a newcomer to the Android OS I personally wouldn't want risking doing something wrong, haha, my heart almost stopped when I ended up having my first boot loop.
Besides, I still don't get it how did the guy in the first post manage to downgrade his HBOOT, isn't that impossible with S-ON? My phone came with 4.4.2 out of the box, at that time I didn't even bother coming to XDA so I just went for an OTA update, haha, which basically rendered my chances of successfully s-offing my device - impossible.
The only reason why I'm eager to wait for Sunshine support to S-Off my device is to try out H/K sound mod. That's it!